Amino acids and esters thereof useful as antihypertensive agents

ABSTRACT

A compound of the formula   &lt;IMAGE&gt;   possesses antihypertensive activity. Also provided are methods for the preparation of the compounds as well as pharmaceutical formulations and methods for their use as antihypertensive agents.

BACKGROUND OF THE INVENTION

This invention relates to antihypertensive agents and to methods fortheir preparation and use. More particularly, it relates toantihypertensive agents comprising substituted alanine compounds and tomethods for the preparation and use of the antihypertensive agents.

DESCRIPTION OF THE PRIOR ART

The art records a long search for agents that are effective in treatinghypertensive patients with acceptable clinical results and few, if any,side effects. There are, of course, a number of products availablecommercially which are useful for this purpose. One that has beenextremely effective for the treatment of hypertension is the L form of3-(3,4-dihydroxyphenyl)-2-methylalanine. This compound and its method ofuse are described in U.S. Pat. No. 3,344,023, issued in 1967. While anumber of other compounds are well known in the art as antihypertensivedrugs, the search continues for even more effective agents.

The compositions of the present invention are also alanine derivativesas are those described above, but are distinctly different in structurefrom prior art compounds.

OBJECTS OF THE INVENTION

It is, accordingly, an object of the present invention to provide newcompounds that are useful as antihypertensive agents.

A further object of the invention is to provide methods for thepreparation of these new compounds.

Another object is to provide pharmaceutical compositions foradministering these substituted alanine compounds.

A still further object of the invention is to provide methods for thetreatment of subjects suffering from hypertension.

These and other objects and advantages of the present invention willbecome apparent from the following description.

SUMMARY OF THE INVENTION

In satisfaction of the foregoing objects and advantages, there areprovided by this invention novel antihypertensive agents of thefollowing general formula: ##STR2## wherein R₁ and R₂ are hydrogen orlower alkyl and R₃ may be: (a) a substituted benzene ring of thefollowing general formula: ##STR3## wherein Y₁ and Y₂ are as specifiedin detail below; or (b) a substituted or unsubstituted benzoheterocyclicring of the following general formula: ##STR4## in which the specificbenzoheterocyclic rings and the substituents are as specified in detailbelow; or (c) a substituted or unsubstituted heterocyclic ring of thefollowing general formula: ##STR5## in which the heterocyclic rings andthe substituents thereon are as specified in detail below.

The foregoing general formulas are intended to include the racemicmixtures, the D and L enantiomorphs, and the pharmaceutically acceptablecarboxylate salts and acid addition salts. Also provided are methods forthe preparation of the compounds of the foregoing general formulas aswell as pharmaceutical formulations, and methods for their use in thetreatment of subjects suffering from hypertension to effect bloodpressure lowering in these subjects.

DETAILED DESCRIPTION

As pointed out above, the invention is concerned with newantihypertensive agents which have been found to have significantantihypertensive activity and thus are very suitable for lowering theblood pressure of subjects suffering from hypertension. Theantihypertensive agents may be best described as comprising a compoundof the following general structural formula: ##STR6## wherein R₁ and R₂may be hydrogen or alkyl of from 1 to 3 carbon atoms, and R₃ may be: (a)a substituted benzene ring of the following general formula: ##STR7##wherein Y₁ and Y₂ are the same or different and are selected fromhydrogen, cyanoamino, carboxyl, cyano, thiocarbamoyl, aminomethyl,guanidino, hydroxy, methanesulfonamido, nitro amino, methanesulfonyloxy,carboxymethoxy, or methoxy or a substituted or unsubstituted 5-memberedheterocyclic ri benzoheterocyclic or dibenzoheterocyclic ring containingone or more nitrogen or sulfur atoms. Specific examples of suchheterocyclic rings are pyrrol-1-yl, 2-carboxypyrrol-1-yl,2-amino-imidazol-1-yl, imidazol-2-ylamino, indol-1-yl, carbazol-9-yl,4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl,4-trifluoromethylthiazol-2-yl, imidazol-2-yl and4,5-dihydroimidazol-2-yl; or (b) a substituted or unsubstitutedbenzoheterocyclic ring of the following general formula: ##STR8## inwhich the benzoheterocyclic ring is selected from indolin-5-yl,1H-2-oxindol-5-yl, indol-5-yl, 2-mercaptobenzimidazol-5(6)-yl,2-aminobenzimidazol-5(6)-yl, 2-methanesulfonamidobenzimidazol-5(6)-yl,1H-benzoxazol-2-on-6-yl, 2-aminobenzothiazol-6-yl, 2,1,3-benzothiadiazol-5-yl,1,3-dihydro-2,2-dioxo-2,1,3-benzothiadiazol-5-yl,1,3-dihydro-1,3-dimethyl-2,2-dioxo-2,1,3-benzothiadiazol-5-yl,4-methyl-2(1H)-oxoquinolin-6-yl, quinoxalin-6-yl,2-hydroxyquinoxalin-6-yl, 2-hydroxquinoxalin-7-yl,2,3-dihydroxyquinoxalin-6-yl and2,3-dihydro-3(4H)-oxo-1,4-benzoxazin-7-yl; or (c) a substituted orunsubstituted heterocyclic ring of the following general formula:##STR9## in which the heterocyclic ring is selected from5-hydroxy-4H-pyran-4-on-2-yl, 2-hydroxypyrid-4-yl, 2-aminopyrid-4-yl, ortetrazolo[1,5-a]pyrid-7-yl.

It is to be understood that the present invention is directed to notonly the racemic mixtures, but also the D and L enantiomorphs. Also theinvention is inclusive of the pharmacologically acceptable carboxylatesalts such as those of Na, K, Ca and NH₄ and the pharmacologicallyacceptable acid-addition salts formed with pharmaceutically acceptableacids.

Specific compounds of the present invention include the following:

4-cyanoamino-α-methylphenylalanine

3-carboxy-α-methylphenylalanine

α-methyl-4-thiocarbamoylphenylalanine

4-(aminomethyl)-α-methylphenylalanine

4-guanidino-α-methylphenylalanine

3-hydroxy-4-methanesulfonamido-α-methylphenylalanine

4-amino-3-methanesulfonyloxy-α-methylphenylalanine

3-carboxymethoxy-4-nitro-α-methylphenylalanine

4-amino-α-methyl-3-nitrophenylalanine

3,4-diamino-α-methylphenylalanine

α-methyl-4-(pyrrol-1-yl)phenylalanine

4-(2-aminoimidazol-1-yl)-α-methylphenylalanine

4-(imidazol-2-ylamino)-α-methylphenylalanine

4-(4,5-dihydro-4-hydroxy-4-trifluoromethyl-thiazol-2-yl)-α-methylphenylalanine

α-methyl-4-(4-trifluoromethylthiazol-2-yl)phenylalanine

α-methyl-3-(4-trifluoromethylthiazol-2-yl)-phenylalanine

3-cyano-α-methylphenylalanine

α-methyl-3-(4-trifluoromethylthiazol-2-yl)tyrosine

4-(imidazol-2-yl)-α-methylphenylalanine

4-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine

3-(imidazoly-2-yl)-α-methylphenylalanine

3-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine

4-(imidazol-2-yl)phenylalanine

4-(4,5-dihydroimidazol-2-yl)phenylalanine

3-(imidazol-2-yl)phenylalanine

3-(2,3-dihydro-1H-indol-5-yl)-α-methylalanine

α-methyl-3-(1H-2-oxindol-5-yl)alanine

3-(1H-indol-5-yl)-α-methylalanine

3-(benzimidazol-2-thione-5-yl)-α-methylalanine

3-(2-aminobenzimidazol-5-yl)-2-methylalanine

2-methyl-3-(benzoxazol-2-on-6-yl)alanine

3-(2-aminobenzothiazol-6-yl)-2-methylalanine

3-(2-aminobenzothiazol-6-yl)alanine

2-methyl-3-(2,1,3-benzothiadiazol-5-yl)-alanine

3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine 2,2-dioxide

3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-alanine 2,2-dioxide

3-(1,3-dihydro-1,3-dimethylbenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine2,2-dioxide

α-methyl-3-[4-methyl-2(1H)-oxoquinolin-6-yl]alanine

3-[4-methyl-2(1H)-oxoquinolin-6-yl]alanine

2-methyl-3-(quinoxalin-6-yl)alanine

2-methyl-3-(2-hydroxyquinoxalin-6-yl)alanine

2-methyl-3-(2-hydroxyquinoxalin-7-yl)alanine

3-(2,3-dihydroxyquinoxalin-6-yl)-2-methylalanine

3-(quinoxalin-6-yl)alanine

3-(2,3-dihydroxyquinoxalin-6-yl)alanine

3-(1,4-benzoxazin-3-one-7-yl)-2-methylalanine

3-(1,4-benzoxazin-3-one-7-yl)alanine

3-(5-hydroxy-4H-pyran-4-on-2-yl)-2-methylalanine

3-(2-hydroxy-4-pyridyl)-2-methylalanine

3-cyano-α-methyltyrosine

4-(pyrrol-1-yl)phenylalanine

4-[2-(carboxy)pyrrol-1-yl]phenylalanine

α-methyl-3-(pyrrol-1-yl)phenylalanine

3-hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalanine

3-methoxy-α-methyl-4-(pyrrol-1-yl)phenylalanine

α-methyl-3-(pyrrol-1-yl)tyrosine

4-methoxy-α-methyl-3-(pyrrol-1-yl)phenylalanine

4-(indol-1-yl)-α-methylphenylalanine

4-(carbazol-9-yl)-α-methylphenylalanine

3-(imidazol-2-yl)-α-methyltyrosine

2-methyl-3-(2-methanesulfonylamidobenzimidazol-5-yl)alanine

2-methyl-3-(2-amino-4-pyridyl)alanine

2-methyl-3[tetrazolo(1,5-a)-pyrid-7-yl]alanine

The compounds of the present invention have been found to be effectivein reducing elevated blood pressure in mammalian species, e.g., rats,and so are useful as antihypertensive agents. The compounds of thepresent invention are active either per se or in combination withα-hydrazino-α-loweralkyl-3,4-dihydroxyphenyl propionic acid or its saltsor lower alkyl esters which compounds are themselves ineffective inreducing blood pressure in mammalian species. The compounds of thepresent invention may be administered either orally or parenterally andthey can be compounded by the usual pharmaceutical methods for use inthe lowering of blood pressure in subjects suffering from hypertension.Dosage units for the compounds may vary from about 0.05 to about 100 mgper kg per day. Normal dosage units for the compounds for oraladministration will vary from about 10 to about 500 mg per kg per day.For oral administration to humans the dosage range is from about 0.1 toabout 5 grams per day, preferably from about 0.5 to about 1.5 grams perday, usually in small but frequent dosages, e.g., in from 1 to 4 dosesper day.

The antihypertensive agents of the present invention in the describeddosages may be administered orally, however, other routes such asintraperitoneally, subcutaneously, intramuscularly or intravenously, maybe employed.

For oral therapeutic administration, the active compounds of thisinvention may be incorporated with excipients and used in the form oftablets, troches, capsules, elixirs, suspensions, syrups, wafers,chewing gums, and the like. The amount of active compound in suchtherapeutically useful compositions or preparations is such that asuitable dosage will be obtained.

For the compounds of the present invention not active per se, effectiveblood pressure lowering activity is obtained by administering them inthe presence of from about 0.005 to about 200 mg per kg ofα-hydrazino-α-loweralkyl-3,4-dihydroxyphenyl propionic acid or its saltsor lower alkyl esters.

The tablets, troches, pills, capsules and the like may also contain thefollowing: a binder such as gum tragacanth, acacia, corn starch orgelatin; and excipients such as dicalcium phosphate; a disintegratingagent such as corn starch, potato starch, alginic acid and the like; alubricant such as magnesium stearate; and a sweetening agent such assucrose, lactose or saccharin may be added or a flavoring agent such aspeppermint, oil of wintergreen, or cherry flavoring. Various othermaterials may be present as coatings or to otherwise modify the physicalform of the dosage unit, for instance, tablets, pills or capsules may becoated with shellac, sugar, or both. A syrup or elixir may contain theactive compounds, sucrose as a sweetening agent, methyl and propylparabens as preservatives, a dye and a flavoring such as cherry ororange flavor. Of course, any material used in preparing any dosage unitform should be pharmaceutically pure and substantially non-toxic in theamounts employed.

As to the pharmaceutically acceptable salts, those coming within thepurview of this invention include the pharmaceutically acceptableacid-addition salts. Acids useful for preparing these acid-additionsalts include, inter alia, inorganic acids, such as hydrochloric,hydrobromic, sulfuric, and phosphoric acids, and organic acids such asmaleic, fumaric, tartaric, citric, 2-acetoxybenzoic, salicylic,succinic, or methanesulfonic acids. Also included within the inventionare the pharmacologically acceptable carboxylate salts such as those ofNa, K, Ca and NH₄.

The following examples illustrate the present invention without,however, limiting the same thereto. Unless indicated otherwise, alltemperatures are expressed in degrees Celsius.

EXAMPLE 1 D,L-4-Cyanoamino-α-methylphenylalanine hydrate

To a solution of 3.2 g. (12 mmoles) of D,L-4-amino-α-methylphenylalaninedihydrochloride [Saari, et al., J. Med. Chem., 10, 1008 (1967)] and 5.05g. (63 mmoles) of sodium acetate in 25 ml of water is added 1.6 g (15mmoles) of cyanogen bromide. After 30 minutes a fine white solid beginsto separate, and 0.5 g. (5 mmoles) more of cyanogen bromide is added andthe mixture left at room temperature for 16 hours. The product, whichhas crystallized, is obtained by filtration, washed with water anddried. Yield 2.02 g. (77%), m.p. 370°.

EXAMPLE 2 DL-3-carboxy-α-methylphenylalanine Hydrochloride A. MethylD,L-3-(3-cyanophenyl)-2-isocyano-2-methyl propionate

Methyl 2-isocanopropionate (43.5 g, 385 mm) is added slowly to asuspension of sodium methoxide (20% excess) in 225 ml of drydimethylformamide at -10° to -15°. The resultant solution is addedslowly to a solution of 63 g 320 mmoles) of 3-cyanobenzyl bromide [J.von Braun and H. Reich, Ann. 445, 225 (1925)] in 200 ml of drydimethylformamide at -10° to -15°. After the addition is complete thereaction mixture is allowed to reach room temperature. The mixture isadded with stirring to a mixture of ice and water and the solid isfiltered. The solid is suspended in 200 ml of water. The suspension isstirred for 1 hour, filtered, rinsed with water and dried in the air toyield methyl D,L-3-(3-cyano-phenyl)-2-isocyano-2-methyl propionate (56g, 77%) m.p. 77°-80°.

B. DL-3-carboxy-α-methylphenylalanine Hydrochloride

The product from part A (4.0g) and 35 ml of 12N hydrochloric acid isrefluxed for 6 hours and the resulting white solid filtered, washed anddried to give the product as the hydrochloride salt (4.1 g, 90%) m.p.280°-285° (dec.).

EXAMPLE 3 D,L-α-methyl-4-thiocarbamoylphenylalanine methyl ester A.Methyl D,L-3-(4-cyanophenyl)-2-isocyano-2-methyl propionate

Methyl 2-isocyanopropionate (43.5 g, 385 mmoles) is added slowly to asuspension of sodium methoxide (20% excess) in 225 ml of drydimethylformamide at -10° to -15°. The resultant solution is addedslowly to a solution of 49.0 g (0.25 mole) of 4-cyanobenzyl bromide[Case, J. Am. Chem. Soc., 47, 1143 (1925)] in 200 ml of dry dimethylformamide at -10° to -15°. After the addition is complete the reactionmixture is allowed to reach room temperature. The mixture is added withstirring to a mixture of ice and water and the solid is filtered. Thesolid is suspended in 200 ml of water, stirred for 1 hour, filtered,rinsed with water and dried in the air to yield methylD,L-3-(4-cyanophenyl)-2-isocyano-2-methyl propionate (45.5 g, 80%) m.p.90°-91°.

B. D,L-4-cyano-N-formyl-α-methylphenylalanine methyl ester

Methyl D,L-3-(4-cyanophenyl)-2-isocyano-2-methyl propionate (50 g 0.22mole), prepared as described in step A is dissolved in 500 ml of ethylacetate. To the resultant solution four milliliters of concentratedhydrochloric acid is added and the mixture is stirred at roomtemperature for 10-15 minutes. The ethyl acetate solution is rinsed withwater until neutrality, dried, filtered and evaporated to dryness. Theoily residue is tritutated with ether and allowed to crystallize. Thesolid is filtered, rinsed with cold ether and dried in the air to yieldD,L-4-cyano-N-formyl-α-methyl phenylalanine methyl ester, 32.7 g (60%),m.p. 152°-153°.

C. D,L-4-N-formyl-α-methyl-4-thiocarbamoylphenylalanine methyl ester

D,L-4-cyano-N-formyl-α-methylphenylalanine methyl ester (5.0 g, 20.3mmoles) is dissolved in 150 ml of pyridine. To the resultant solutiontriethylamine (2.1 g) is added and hydrogen sulfide is bubbled throughthe solution for 2 hours. The mixture is stirred for 18 hours at roomtemperature, evaporated to dryness and the residue is dissolved inchloroform. The chloroform solution is rinsed with water, dried,filtered and evaporated to dryness to yield a gum. A layer of ether isadded on top of the gum and the mixture is allowed to crystallize atroom temperature for 48 hours. The solid is filtered, rinsed with etherand dried in the air to giveD,L-N-formyl-α-methyl-4-thiocarbamoylphenylalanine methyl ester. 5.36 g(94%), m.p. 135°-137°.

D. D,L-α-methyl-4-thiocarbamoylphenylalanine methyl ester

To a solution (4.4g, 15.7 mmoles) ofD,L-N-formyl-α-methyl-4-thiocarbamoylphenylalanine methyl ester in 120ml of methanol is added 5 ml of concentrated hydrochloric acid and themixture is left to stand at room temperature for 3 days. The solution isevaporated to dryness, the residue dissolved in 100 ml of water which iswashed with 2 × 50 ml of ethyl acetate. The aqueous phase is made basicwith sodium bicarbonate, and extracted with 2 × 100 ml of ethyl acetate.The ethyl acetate extracts are dried, evaporated and the residuetriturated with 15 ml of ether and the resulting solid filtered to yield3.6 g (76%) of D,L-α-methyl-4-thiocarbamoylphenylalanine methyl ester,m.p. 126°-128°.

EXAMPLE 4 D,L-4-(aminomethyl)-α-methylphenylalanine dihydrochloridehydrate

A mixture of 6.0 g (24.4 mmoles) ofD,L-4-cyano-N-formyl-α-methylphenylalanine methyl ester (prepared asdescribed in step B of Example 3), 1.0 gm of Raney nickel and 150 ml ofacetic anhydride is hydrogenated under 18.1 kg of hydrogen for a periodof 6 hours. The reaction mixture is filtered from the catalyst and thefiltrate evaporated to leave a thick oil which is heated to reflux in150 ml of concentrated hydrochloric acid for 6 hours. The solution isevaporated to dryness and from the residue 3 × 50 ml of water and 4 × 55ml of benzene are evaporated successively. The solid residue is finallyfiltered with aid of benzene and dried to give 6.15 g (90%) ofD,L-4-(aminomethyl)-α-methylphenylalanine dihydrochloride hydrate, m.p.178°-186° (dec.).

EXAMPLE 5 D,L-4-Guanidino-α-methylphenylalanine Dihydrochloride A.D,L-N-acetyl-α-methyl-4-aminophenylalanine methyl ester

D,L-N-acetyl-α-methyl-4-nitrophenylalanine methyl ester, [Zenker et al.,J. Med. Chem., 17, 1223 (1974)], (40 g, 143 mm) in methanol ishydrogenated at 3.1 kg/cm² over 5% palladium on charcoal. The solutionis filtered and concentrated to yield 15.8 g ofD,L-N-acetyl-α-methyl-4-aminophenylalanine methyl ester, m.p. 145°-148°.The mother liquors are evaporated to yield a further 17.8 g ofN-acetyl-60-methyl-4-aminophenyl alanine methyl ester. Total yield 94%.

B. D,L-N-Acetyl-4-(3-benzoylguanidino)-α-methylphenylalanine methylester

D,L-N-Acetyl-α-methyl-4-aminophenylalanine methyl ester (3.0 g, 12mmoles) is dissolved in 50 ml of methanol, dry hydrogen chloride ispassed into the solution, and the solvent is removed in vacuo. Theevaporation is repeated several times with methanol. The residue isdissolved in 25 ml of methanol and then refluxed for 24 hours with 1.76g (12 mmoles) of benzoyl cyanamide. A further 352 mg (2 mmole) ofbenzoyl cyanamide is added and the solution refluxed a further 24 hours.The solution is evaporated in vacuo and the solids triturated with ethylacetate to give 4.75 g of solids. The solids are further triturated with50 ml of hot ethyl acetate to give 4.12 g (79.2%) ofD,L-N-acetyl-4-(3-benzoylguanidino)-α-methyl-phenylalanine methyl ester,m.p. 234°-245° (dec).

C. D,L-4-guanidino-α-methylphenylalanine dihydrochloride

D,L-N-acetyl-4-(3-benzoylguanidino)-α-methylphenylalanine methyl ester(3.45 g, 8 mmole) is refluxed for 6 hours in 160 ml. of 7N hydrochloricacid. The solution is extracted with 3 × 20 ml of diethyl ether toremove benzoic acid and the aqueous portion is evaporated. The residueis treated with 1:1 ethanol:benzene to afford a dry product, and finallytriturated with hot ethanol to give 1.53 g (61.9%) ofD,L-4-guanidino-α-methylphenylalanine dihydrochloride, m.p. 299°-303°(dec).

EXAMPLE 6 D,L-3-Hydroxy-4-methanesulfonamido-α-methylphenylalanine A.D,L-N-Formyl-3-hydroxy-4-nitro-α-methylphenylalanine methyl ether

In a 3 liter, 3-neck flask, equipped with a mechanical stirrer, dryingtube and thermometer, 3-hydroxy-4-nitro benzyl chloride (140.5 g, 0.75mole), prepared as described by S. B. Hanna et al., J. Chem. Soc. 221,(1961) is dissolved in dimethyl formamide (750 ml). The solution iscooled in an ice-bath and powdered sodium methoxide (40.5 g, 0.75 mole)is added over a 5-minute period. This flask is then cooled andmaintained at -55°. In a separate flask, to a suspension of sodiummethoxide (81 g, 1.5 moles) in dimethyl formamide (1.0 liter) kept at-55°, is added methyl 2-isocyanopropionate (171 g, 1.5 moles). Thetemperature is not allowed to rise above -50°. This solution is thenadded to the flask containing the anion of 3-hydroxy-4-nitrobenzylchloride, always keeping the temperature at -50°. Over a period of 30minutes, the temperature is allowed to reach -35° after which TLCanalysis indicates complete disappearance of 3-hydroxy-4-nitrobenzylchloride. Water (1000 ml) is then added and the mixture is extractedthree times with ether to remove excess methyl 2-isocyanopropionate. Theaqueous phase is acidified by addition of acetic acid (180 ml in 180 mlof water) and is extracted three times with ether. The organic phase iswashed with water, dried over magnesium sulfate and concentrated undervacuum. The residual oil, dissolved in ethyl acetate (1.5 liters) andmaintained at 0°, is hydrolyzed by adding concentrated hydrochloric acid(15 ml) and stirring for a period of 10 minutes. The solution is washedwith water, dried over magnesium sulfate and concentrated under vacuumto yield 155 g (73%) of a solid after trituration in petroleum ether,m.p. 113°-115°.

B. D,L-3-Hydroxy-4-methanesulfonamido-α-methylphenylalanine

D,L-N-Formyl-3-hydroxy-4-nitro-α-methylphenylalanine methyl ester (14.1g, 50 mmoles) dissolved in 50 ml methanol is hydrogenated over 5%palladium on charcoal on a Parr hydrogenator. After the absorption ofhydrogen is over, the catalyst is filtered off and the solvent isevaporated under vacuum, leaving a thick red oil that is dissolved inacetone (200 ml) and water (20 ml). Methanesulfonyl chloride (22.2 g,195 mmole) and potassium carbonate (27 g, 195 mmoles) are added and thereaction mixture is stirred for a period of 1 hour. The insolubles arefiltered and washed with acetone. The filtrate is concentrated to yielda dark oily residue which is taken up in ethyl acetate, washed withdilute hydrochloric acid and with water. The organic layer is dried overmagnesium sulfate and concentrated. The residue (6 g) is absorbed on asilica gel column and eluted with ethyl acetate yielding 5.5 g of aresidue consisting ofD,L-N-formyl-4-bis(methanesulfonyl)amino-3-methanesulfonyloxy-α-methylphenylalaninemethyl ester. It is taken up in 50 ml of 5% sodium hydroxide and heatedon a steam bath for 2 hours. The pH of the solution is adjusted toneutrality and the solution is passed through a Dowex 50W-X8 100-200mesh H⁺ charged column. Elution with 5% ammonium hydroxide yields 1.64 g(11.4%) of D,L-3-hydroxy-4-methanesulfonamido-α-methylphenylalanine,m.p. 298° (dec.).

EXAMPLE 7 D,L-4-Amino-3-methanesulfonyloxy-α-methylphenylalaninedihydrochloride A.D,L-N-Formyl-3-methanesulfonyloxy-4-nitro-α-methylphenyl alanine methylester

To D,L-N-formyl-3-hydroxy-4-nitro-α-methylphenylalanine methyl esterprepared as in step A of Example 6 (5.64 g, 20 mmoles) in 100 ml acetoneand 10 ml water is added methanesulfonyl chloride (5.56 g, 40 mmoles)and potassium carbonate (5.52 g, 40 mmoles). The mixture is stirred atroom temperature for 15 minutes. The insolubles are filtered off andwashed well with acetone. The filtrate is evaporated to a small volume,ether is added and the solution is washed three times with water. Afterthe third washing, a solid crystallizes out and is filtered to yield 5.8g (80%) ofD,L-N-formyl-3-methanesulfonyloxy-4-nitro-α-methylphenylalanine methylester, m.p. 132°-134°.

B. D,L-4-amino-3-methanesulfonyloxy-α-methylphenylalaninedihydrochloride

D,L-N-Formyl-3-methaneslfonyloxy-4-nitro-α-methyl phenylalanine methylester (4.5 g, 12.5 mmoles) from step A, in 50 ml concentratedhydrochloric acid is heated on a steam bath for 3.5 hours. The reactionmixture is evaporated to dryness to leave 4.6 g of a residue that isdissolved in 30 ml concentrated hydrochloric acid. Stannous chloridedihydrate (19.5 g, 87 mmoles) in 30 ml concentrated hydrochloric acid isadded to this solution. The mixture is heated on the steam bath for 1hour and is then poured into 500 ml water. Hydrogen sulfide is bubbledthrough the solution to remove all tin ions. The insoluble tin sulfidesare filtered and the filtrate is evaporated to dryness. Refluxing theresidue in toluene to remove traces of water gives 3.6 g (80%)D,L-3-methanesulfonyloxy-4-amino-α-methylphenylalanine dihydrochloride,m.p. 162° (dec.).

EXAMPLE 8 D,L-3-Carboxymethoxy-4-nitro-α-methylphenylalanineHydrochloride

To D,L-N-formyl-3-hydroxy-4-nitro-α-methylphenylalanine methyl ester(prepared as in step A of Example 6) (2.8 g, 10 mmoles) in 10 mldimethyl formamide is added potassium t-butoxide (1.5 g, 13.2 mmoles)while the temperature is maintained at 10° with an ice bath. Ethylbromoacetate (1.8 g, 10.8 mmoles) in 10 ml dimethylformamide is thenadded dropwise and the resulting mixture is stirred for 3 hours at roomtemperature, and then poured onto 700 ml ether and washed several timeswith water. After drying over magnesium sulfate and concentration undervacuum, an oily residue (4.2 g) is obtained. A rapid purification byobsorbing on silica gel and eluting with chloroform yields 3.8 g (92%)of D,L-N-formyl-3-carboethoxymethoxy-4-nitro-α-methylophenylalaninemethyl ester. This intermediate (2.8 g, 7.8 mmoles) in 25 mlconcentrated hydrochloric acid is heated on a steam bath for 2 hours.The volatiles are removed under vacuum and the residue is treated withtoluene yielding 2.2 g (88%) ofD,L-3-carboxymethoxy-4-nitro-α-methylphenylalanine hydrochloride, m.p.250° (dec.).

EXAMPLE 9 D,L-4-Amino-α-methyl-3-nitrophenylalanine Dihydrochloride A.D,L-N-Acetyl-α-methyl-4-amino-3-nitrophenylalanine methyl ester

D,L-N-Acetyl-α-methyl-4-acetylamino-2-nitrophenyl-alanine methyl ester[Zenker et al., J. Med. Chem., 17, 1223, (1974)] (45.9 g, 0.136 moles)and sodium carbonate (17.3 g, 0.163 moles) in 75% methanol-water (1500ml) are stirred at room temperature for 18 hours. The resultingprecipitate is filtered and slurried with water to yield 34.4 g (86%) ofD,L-N-acetyl-α-methyl-4-amino-3-nitrophenylalanine methyl ester, m.p.189°-192°.

B. D,L-4-Amino-α-methyl-3-nitrophenylalanine Dihydrochloride

A mixture of 10.0 g (34 mmoles) of the product from step A and 150 ml of12N hydrochloric acid is heated in a sealed glass reaction vessel at135° for 1 hour. The reaction mixture is then evaporated to dryness andthe residue further dried by repeated evaporation of benzene. Theresulting residue is slurried with ether and filtered to give 10.36 g(98%) of D,L-4-amino-α-methyl-3-nitrophenylalanine dihydrochloride m.p.239°-241° (dec.).

EXAMPLE 10 D,L-3,4-Diamino-α-methylphenylalanine Dihydrochloride

A mixture of 4.7 g (15 mmoles) ofD,L-4-amino-α-methyl-3-nitrophenylalanine dihydrochloride (prepared asin step B of Example 9), 500 mg. of 10% palladium on charcoal and 250 mlof methanol is hydrogenated under 18 kg pressure for 1 hour. Thereaction mixture is filtered, evaporated to dryness and the residuerefluxed in toluene for 16 hours. Filtration and drying gives 3.3 g ofD,L-3,4-diamino-α-methylphenylalanine dihydrochloride, m.p. 135°-140°(dec.).

A. EXAMPLE 11 D,L-α-Methyl-4-(pyrrol-1-yl)phenylalanineD,L-N-formyl-α-methylphenylalanine methyl ester

Treating 35 g (153 mmoles) of D,L-α-methylphenylalanine methyl esterhydrochloride according to the method of Stein et al., J. Am. Chem.soc., 77, 700 (1955), except substituting a formic-acetic anhydridemixture for acetic anhydride, there is obtained 27 g (80%) ofD,L-N-formyl-α-methyl-phenylalanine methyl ester, m.p. 64°.

B. D,L-N-Formyl-α-methyl-4-nitrophenylalanine methyl ester

The product from step A, 10 g (45.3 mmoles), is added slowly to 25 ml ofstirring HNO₃ (red, fuming) at -15°. After stirring for an additionalhour at -15°, the mixture is added slowly to a vigorously stirred,ice-cold, saturated NaHCO₃ solution. The resulting precipitate isfiltered, washed with H₂ O, and washed with 25 ml of ether yielding 4.24g, m.p. 108°. The mother liquors yield another 7.0 g (oil) of crudeproduct. The total yield is 94%.

C. D,L-N-formyl-α-methyl-4-amino-phenylalanine methyl ester

D,L-N-formyl-α-methyl-4-nitrophenylalanine methyl ester 184 g (690mmoles) in methanol is hydrogenated at 3.1 kg/cm² over 5% palladium oncharcoal. The solution is filtered and evaporated to yield a gum. Thegum is dissolved in 2N hydrochloric acid and extracted with ethylacetate.

The acidic aqueous solution is rendered alkaline with sodium bicarbonateand extracted with ethyl acetate. The ethyl acetate solution isevaporated and the residue is crystallized from methanol to yield 79.5 g(48.5%) of D,L-N-formyl-α-methyl-4-aminophenylalanine methyl ester, m.p.105°-108°.

D. D,L-N-formyl-α-methyl-4-(pyrrol-1-yl)phenylalanine methyl ester

A solution of 13.5 g (57 mmoles) ofD,L-N-formyl-α-methyl-4-aminophenylalanine methyl ester (prepared as instep C) and 8.44 g (64 mmoles) of 2,5-dimethoxytetrahydrofuran in 60 mlof acetic acid is heated on the steam bath under nitrogen for 30minutes. The mixture is cooled, 150 ml of water added and the aqueousmixture extracted with 6 × 150 ml of chloroform. The combined chloroformextracts are washed with water, dried over magnesium sulfate, filtered,and the filtrate evaporated to dryness in vacuo to give 19.4 g of crudeproduct. The crude residue is eluted from a silica gel column withchloroform and the residue after the removal of chloroform is trituatedwith low boiling petroleum ether to give 8.32 g (50%) ofD,L-N-formyl-α-methyl-4-(pyrrol-1-yl)phenylalanine methyl ester, m.p.118°-119°.

E. D,L-α-methyl-4-(pyrrol-1-yl)phenylalanine

D,L-N-formyl-α-methyl-4-(pyrrol-1-yl)phenylalanine methyl ester (7.9 g,27.6 mmoles) is heated overnight under nitrogen on a steam bath in 75 mlof methanol and 16 ml of 7N sodium hydroxide solution. A further 4 ml of7N sodium hydroxide solution is added and the solution is heated fourhours longer on the steam bath. The mixture is evaporated in vacuo, thesolid residue dissolved in 100 ml of water, and 6.78 g (113 mmoles) ofacetic acid is added. The mixture is refrigerated and the solidscollected. The solids are refluxed for 1 hour with water, filtered, thesolids washed with ethanol, then diethyl ether, and dried for severalhours in a vacuum oven at 60° to give 6.45 g (79.5%) ofD,L-α-methyl-4-(pyrrol-1-yl) phenylalanine, m.p. 290°-293° (dec.).

EXAMPLE 12 D,L-4-(2-Aminoimidazol-1-yl)-α-methylphenylalaninehydrochloride and D,L-4-(imidazol-2-yl)-α-methylphenylalaninehydrochloride A. D,L-N-Acetyl-4-cryanamido-α-methylphenylalanine methylester

D,L-N-Acetyl-4-amino-α-methylphenylalanine methyl ester (16 g, 64mmoles) (prepared as in step A of Example 5) is suspended in 225 ml ofwater, then 4.8 ml of concentrated hydrochloric acid in 25 ml of wateradded, followed by 12.7 g (155 mmoles) of sodium acetate, and finally by13.6 g (128 mmole) of cyanogen bromide. The mixture is left at roomtemperature for 0.5 hour during which time much solids are precipitated.The solids are collected and air dried to give 16.8 g (95.2%) ofD,L-N-acetyl-4-cyanamido-α-methylphenylalanine methyl ester, m.p.171.5°- 173.5°.

B. D,L-N-Acetyl-α-methyl-4-thioureidophenylalanine methyl ester

D,L-N-Acetyl-4-cyanamido-α-methylphenylalanine methyl ester (16.8 g, 61mmole) is dissolved in a solution of 350 ml of dry pyridine and 6.8 g(67.1 mmoles) of triethylamine. Dry hydrogen sulfide is passed on during2 hours accompanied by stirring. The solvent is removed in vacuo, theresidue triturated with chloroform, filtered, and dried to give 18.4 g(97.5%) of D,L-N-acetyl-α-methyl-4-thioureidophenylalanine methyl ester,m.p. 202°-204°.

C. D,L-N-Acetyl-α-methyl-4-(2-methyl-1-isothioureido)phenylaanine methylester

D,L-N-Acetyl-α-methyl-4-thioureidophenylalanine methyl ester (18.3 g, 59mmole) is suspended in 350 ml of acetonitrile and treated with 7.4 g(64.9 mmole) of methyl fluorosulfonate. The mixture is stirred for 1hour to effect solution. The solution is concentrated in vacuo and theresidue partitioned between ethyl acetate and dilute sodium bicarbonate.The ethyl acetate extracts are dried over magnesium sulfate, evaporatedto dryness, and the residue crystallized from ethyl acetate-diethylether to give 15.4 g (80.7%) ofD,L-N-acetyl-α-methyl-4-(2-methyl-1-isothioureido) phenylalanine methylester, m.p. 156°-158.0° (dec.).

D. D,L-4-(2-Aminoimidazol-1-yl)-α-methylphenylalanine hydrochloride andD,L-4-(imidazol-2-ylamino)-α-methylphenylalanine hydrochloride

D,L-N-Acetyl-α-methyl-4-(2-methyl-1-isothioureido)-phenylalanine methylester (15 g, 47.6 mmoles) is heated for 14 hours at 83° with 63.3 g (476mmoles) of 2-aminoacetaldehyde diethyl acetal. Excess of the acetal isremoved by distillation in vacuo to give 20 g (ca theory) ofD,L-N-acetyl-4-[2-(2,2-diethoxyethyl)guanidinophenylalanine methyl esteras an oil. This product is used without further purification in the nextreaction.

D,L-N-Acetyl-4-[2-(2,2-diethoxyethyl)guanidino]-phenylalanine methylester (ca 20 g) is dissolved in 200 ml of 6N hydrochloric acid at roomtemperature and the solution is immediately evaporated to dryness invacuo at a bath temperature maintained at 45°. The residue is dissolvedin water, treated with ammonium hydroxide to a pH of 10, then extractedwith chloroform, and the combined chloroform extracts dried overmagnesium sulfate. The filtrate is evaporated and the residuecrystallized from acetonitrile to afford 2.75 g ofD,L-N-acetyl-4-(2-aminoimidazol-1-yl)-α-methylphenylalanine methyl ester(containing a small amount of its isomer), m.p. 179°-183°. This ester(2.75 g) is refluxed for 5 hours in 55 ml of concentrated hydrochloricacid to give 2.33 g ofD,L-4-(2-aminoimidazol-1-yl)-α-methylphenylalanine hydrochloride[containing ca 10% of D,L-4-(imidazol-2-ylamino)-α-methylphenylalaninehydrochloride].

The residues obtained after removal of the crystallineD,L-N-acetyl-4-(2-aminoimidazol-1-yl)-α-methylphenylalanine methyl esterare refluxed for 6 hours in 125 ml of concentrated hydrochloric acid,then the solvent removed in vacuo, and the product triturated withethanol. The ethanol extracts when treated with benzene, afford 424 mgof D,L-4-(imidazol-2-ylamino)-α-methylphenylalanine hydrochloride, m.p.above 360° (darkening over a wide range). The residues on furtherpurification afford 6.2 g of a mixture of the hydrochlorides ofD,L-4-(2-aminoimidazol-1-yl)-α-methylphenylalanine andD,L-4-(imidazol-2-ylamino)-α-methylphenylalanine.

The ammoniacial liquors from the initial acid hydrolysis are evaporated,the resulting residue dissolved in 125 ml of concentrated hydrochloricacid, and refluxed for 6 hours. The solution is evaporated, the crudeproduct dissolved in ammonia, evaporated, the residue dissolved inwater, and pass through a column of Dowex 50W-X4 50-100 mesh cationexchange resin. The liquid is evaporated to dryness, the solidsdissolved in dilute hydrochloric acid, treated with charcoal, filtered,and partially evaporated to give 1.19 g of pureD,L-4-(2-aminoimidazol-1-yl)-α-methylphenylalanine hydrochloride, m.p.320° (dec). The mother liquors from these solids afford 2.25 g. of 1:1mixture of the hydrochlorides ofD,L-4-(2-aminoimidazol-1-yl)-α-methylphenylalanine andD,L-4-(imidazol-2-ylamino)-α-methylphenylanine.

EXAMPLE 13D,L-4(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-α-methylphenylalaninemethyl ester A.D,L-4-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-N-formyl-.alpha.-methylphenylalaninemethyl ester

To a suspension of 5.0 g (17.8 mmoles) ofD,L-N-formyl-α-methyl-4-thiocarbamoylphenylalanine methyl ester(prepared as in step C of Example 3) in 60 ml of chloroform is added 5 g(26.2 mmoles) of 3-bromo-1,1,1-trifluoroacetone. The starting materialgradually goes into solution and an oil later separates with a slightevolution of heat. The mixture is stirred at 25° for 6 hours, evaporatedto dryness and the residue is partitioned between 50 ml of water and 100ml of ethyl acetate. A second extract of 100 of ethyl acetate iscombined with the first and the whole is dried and evaporated. Theresidue is triturated with 20 ml of ether and the resulting solidfiltered to yield 4.7 g (68%) ofD,L-4-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-N-formyl-.alpha.-methylphenylalaninemethyl ester, m.p. 160°-165°.

B.D,L4-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-α-methylphenylalaninemethyl ester

To a solution of 4.7 g (12 mmoles) ofD,L-4-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-N-formyl-.alpha.-methylphenylalaninemethyl ester in 100 ml of methanol is added 5 ml of concentratedhydrochloric acid and the mixture stirred at 25° for 2 days andevaporated to dryness keeping the temperature below 25°. The residue isdissolved in 100 ml of water and the solution extracted with 100 ml ofethyl-acetate. The aqueous fraction is then made basic with solid sodiumbicarbonate and extracted with 2 × 100 ml of ethyl acetate. The organicsolution is dried and evaporated to leave an oil which on triturationwith 20 ml of low boiling petroleum ether crystallizes. The crystals arerecovered by filtration to yield 2.68 g (62%) ofD,L-4-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl(-α-methylphenylalaninemethyl ester, m.p. 118°-120°.

EXAMPLE 14 D,L-α-Methyl-4-(4-trifluoromethylthiazol-2-yl)phenylalaninehydrochloride

A mixture of 4 g (10.2 mmoles) ofD,L-4-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazoly-2-yl)-N-formyl-.alpha.-methylphenylalaninemethyl ester (prepared as in step A of Example 13) and 50 ml ofconcentrated hydrochloric acid is heated to reflux for 1 hour. Themixture is evaporated to dryness, 50 ml of benzene added and evaporatedand the residue filtered with the aid of 50 ml of benzene. After drying,there is obtained 3.6 g (96%) ofD,L-α-methyl-4-(4-trifluoromethylthiazol-2-yl)phenylalaninehydrochloride, m.p. 220°-230°.

EXAMPLE 15 D,L-α-methyl-3-(4-trifluoromethylthiazol-2-yl)phenylalaninehydrochloride A. D,L-3-cyano-N-formyl-α-methylphenylalanine methyl ester

Methyl D,L-3-(3-cyanophenyl)-2-isocyano-2-methyl propionate (1 g, 4.4mmoles) prepared according to step A of Example 2 is dissolved in 25 mlof ethyl acetate. To the resultant solution one milliliter ofconcentrated hydrochloric acid is added and the mixture is stirred atroom temperature for 10-15 minutes. The ethyl acetate solution is rinsedwith water until neutrality, dried, filtered and evaporated to dryness.The oily residue is triturated with ether and allowed to crystallize.The solid is filtered, rinsed with cold ether and dried in the air toyield D,L-3-cyano-N-formyl-α-methylphenylalanine methyl ester, 830 mg.(77%), m.p. 132°-134°.

B. D,L-N-formyl-α-methyl-3-thiocarbamoylphenylalanine methyl ester

D,L-3-cyano-N-formyl-α-methylphenylalanine methyl ester (25 g, 98.5mmoles) is dissolved in 500 ml of pyridine. To the resultant solutiontriethylamine (10.5 g) is added and hydrogen sulfide is bubbled throughthe solution for two hours. The mixture is stirred for 18 hours at roomtemperature, evaporated to dryness and the residue is dissolved inchloroform. The chloroform solution is rinsed with water, dried,filtered and evaporated to dryness to yield a gum. A layer of ether isadded on top of the gum and the mixture is allowed to crystallize atroom temperature for 48 hours. The solid is filtered, rinsed with etherand dried in the air to giveD,L-N-formyl-α-methyl-3-thiocarbamoylphenylalanine methyl ester, (24.6g, 87%) m.p. 148°-150°.

C.D,L-3-(4,5-Dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-N-formyl-.alpha.-methylphenylalaninemethyl ester

Starting with 5 g (17.8 mmoles) ofD,L-N-formyl-α-methyl-3-thiocarbamoylphenylalanine methyl ester andproceeding according to step A of Example 13, there is obtained 4.97 g(72%) ofD,L-3-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-N-formyl-.alpha.-methyl(phenylalaninemethylester, m.p. 137°-139°.

D. D,L-α-Methyl-3-(4-trifluoromethylthiazoly-2-yl)phenylalaninehydrochloride

Starting with 3.82 g (9.80 mmoles) ofD,L-3-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-N-formyl-.alpha.-methylphenylalaninemethyl ester and carrying out hydrolysis as in Example 14, there isobtained 3.43 g (96%) ofD,L-α-methyl-3-(4-trifluoromethylthiazol-2-yl)-phenylalaninehydrochloride, m.p. 230° (dec.).

EXAMPLE 16 D,L-4-(Imidazol-2-yl)-α-methylphenylalanine dihydrochloridehemihydrate A.D,L-N-Formyl-α-methyl-4-(methylthiocarboximidato)phenylalanine methylester

D,L-N-Formyl-α-methyl-4-thiocarbamoylphenylalanine methyl ester (4.0 g,14.3 mmoles) from step C of Example 3 is dissolved in 120 ml of acetone.Methylfluorosulfonate (1.6 g, 14.25 mmoles) is added and the mixture isstirred at room temperature for 18 hours. The solution is evaporated todryness and the residue is partitioned between water and ethyl acetate.The aqueous layer is extracted twice with 50 ml of ethyl acetate. Theaqueous extract is basified with sodium bicarbonate and extracted withethyl acetate. The ethyl acetate extracts are combined, dried, filteredand evaporated to dryness to yieldD,L-N-formyl-α-methyl-4-(methylthiocarboximidato)phenylalanine methylester, (3 g, 71%), m.p. 119°-120°.

D,L-4-(Imidazol-2-yl)-α-methylphenylalanine dihydrochloride hemihydrate

A mixture of 6.5 g (22 mmoles) ofD,L-N-formyl-α-methyl-4-(methylthiocarboximidato)phenylalanine methylester, 2.0 g (22 mmoles) of oxalic acid and 3.0 g (22.5 mmoles) ofaminoacetaldehyde diethyl acetate in 150 ml of methanol is stirred at25° for 18 hours. The reaction mixture is evaporated to dryness and theresidue dissolved in 100 ml of water. The aqueous solution is extractedwith 50 ml of ethyl acetate which is discarded, made basic with solidsodium bicarbonate and extracted with 2 × 100 ml of ether which isdiscarded. The aqueous solution is then evaporated to dryness to leave agummy residue which is stirred with 500 ml of chloroform for 24 hours.The chloroform solution is filtered to separate inorganic salts, driedand evaporated to leave an oil which is dissolved in 80 ml ofconcentrated hydrocloric acid. The solution is treated at 50° for 30minutes, then heated to reflux for 4 hours. Cooling and filtering of theprecipitated solid yields 2.1 g ofD,L-4-(imidazol-2-yl)-α-methylphenylalanine dihydrochloride hemihydrate,m.p. 225°-230°. Concentration of the filtrate yields a further 0.88 g ofproduct, bringing the yield to 42%.

EXAMPLE 17 D,L-4-(4,5-Dihydroimidazol-2-yl)-α-methylphenylalaninehydrochloride tetrahydrate

A mixture of 3.5 g (11.9 mmoles) ofD,L-N-formyl-α-methyl-4-(methylthiocarboximidato)phenylalanine methylester (prepared as in step A of Example 16 and 2.6 g (12.7 mmoles) of2-bromoethylamine hydrobromide in 100 ml of methanol is stirred at 25°for 23 hours, after which the solvent is evaporated. The residue isredissolved in 100 ml of methanol and 10 g of AG^(R) 1-X8 resin, in thehydroxide form, is added and the mixture stirred at 25° for 4 hours. Thereaction mixture is filtered and the filtrate, upon evaporation todryness, yields 3.2 g of a hygroscopic solid. The solid is dissolved in50 ml of concentrated hydrochloric acid and the solution heated toreflux for 1 hour. The solution is evaporated and the residueredissolved in 50 ml of H₂ O, the solution stirred with 0.5 g ofcharcoal for 30 minutes at 25°, filtered and evaporated to leave a thicksyrup which crystallizes over 24 hours. This solid is slurried with 100ml of ether and filtered to yield 2.76 g (59%) ofD,L-4-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine di-hydrochloridetetrahydrate, m.p. 145°-148° (dec.).

EXAMPLE 18 D,L-3-(Imidazol-2-yl)-α-methylphenylalanine dihydrochloridehydrate A. D,L-N-Formyl-α-methyl-3-(methylthiocarboximidato)-phenylalanine methyl ester

D,L-N-Formyl-α-methyl-3-thiocarbamoylphenylalanine methyl ester (4 g,14.25 mmoles) from step B of Example 15 is dissolved in 120 ml ofacetone. Methylfluorosulfonate (1.6 g, 14.25 mmoles) is added and themixture is stirred at room temperature for 18 hours. The solution isevaporated to dryness, the residue is partitioned between water andethyl acetate. The aqueous layer is extracted twice with 50 ml of ethylacetate. The aqueous extract is basified with sodium bicarbonate andextracted with ethyl acetate. The ethyl acetate extracts are combined,dried, filtered and evaporated to dryness to yieldD,L-N-formyl-60-methyl-3-(thiomethylcarboximidato)phenylalanine methylester, (4.1 g, 97.5%), m.p. 115°-117°.

D,L-3-(Imidazol-2-yl)-α-methylphenylalanine dihydrochloride hydrate

Starting with 9.0 g (30.6 mmoles) ofD,L-N-formyl-α-methyl-3-(methylthiocarboximidato)phenylalanine methylester and proceeding as in step B of Example 16, followed byrecrystallization from 50 ml of water, there is obtained 2.0 g (19%) ofD,L-3-(imidazol-2-yl)-α-methylphenylalanine dihydrochloride hydrate,m.p. 295°-298°.

EXAMPLE 19 D,L-3-(4,5-Dihydroimidazol-2-yl)-α-methylphenylalaninedihydrochloride hydrate

Starting with 5.0 g (17 mmoles) ofD,L-N-formyl-α-methyl-3-(methylthiocarboximadato)phenylalanine methylester (prepared as in step A of Example 18) and proceeding as in Example17, there is obtained 4.23 g (74%) ofD,L-3-(4,5-dihydroimidazol-2-yl)-α-methylalphenylanine dihydrochloridehydrate, m.p. 308-315° (dec.).

EXAMPLE 20 D,L-4-(Imidazol-2-yl)phenylalanine Dihydrochloride Hydrate A.N-Acetyl-4-cyano-α-(ethoxycarbonyl)phenylalanine ethyl ester

To 50 ml dimethylformamide is added 5.7 g (51 mmoles) of potassiumtert-butoxide and 11.1 g (51 mmoles) of diethyl acetamidomalonate andthe resulting mixture stirred at 25° for 15 minutes. The solution isthen cooled to 10° and a solution of 10.0 g (51 mmoles) of 4-cyanobenzylbromide, Case, J. Am. Chem. Soc., 47, 1143, (1925) in 40 ml ofdimethylformamide is added dropwise over 20 minutes. The mixture is thenstirred at 25° for 1 hour after which a further 0.285 g (2.5 mmoles) ofpotassium tert-butoxide and 0.5 (2.5 mmoles) of diethylacetamidomalonate are added and stirring continued for 1 hour at 25°.The reaction mixture is then poured into 300 ml of ice water, causingthe product to precipitate. Filtration, washing with water and dryingyields 10.3 g (31 mmoles, 61%) ofN-acetyl-4-cyano-α-(ethoxycarbonyl)phenylalanine ethyl ester, m.p.160°-163°.

N-acetyl-α-ethoxycarbonyl-4-thiocarbamoylphenylalanine ethyl ester

Into a solution of 10.0 g (30 mmoles) ofN-acetyl-4-cyano-α-(ethoxycarbonyl)phenylalanine ethyl ester and 3.5 g(35 mmoles) of triethylamine in 250 ml of pyridine, hydrogen sulfide gasis introduced until the solution is saturated. The reaction mixture isthen stirred at 25° for 18 hours, followed by evaporation of thesolvent. The residue is slurried with 50 ml of carbon disulfide for 1hour and the resulting crystalline solid recovered by filtration toyield 8.7 g (24 mmoles, 80%) ofN-acetyl-α-ethoxycarbonyl-4-thiocarbamoylphenylalanine ethyl ester, m.p.168°-172°.

C.N-acetyl-α-ethoxycarbonyl-4-(thiomethylcarboximidato)-phenylalanineethylester

To a solution of 8.7 g (24 mmoles) ofN-acetyl-α-ethoxycarbonyl-4-thiocarbamoylphenylalanine ethyl ester in150 ml of acetone is added 1.7 ml (21 mmoles) of methyl fluorosulfonateand the resulting mixture stirred at 25° for 20 minutes. The reactionmixture, containing some precipitate, is then evaporated to dryness and150 ml of water are added to the residue. This mixture is extracted with100 ml of ethyl acetate, the aqueous phase made basic with solid sodiumbicarbonate and extracted again with 2 × 100 ml of ethyl acetate. Thesesecond ethyl acetate extracts are dried, the solvent evaporated and theresidue triturated with 20 ml of ether. The resulting solid is filteredto yield 5.15 g (13.5 mmoles, 56%) ofN-acetyl-α-ethoxycarbonyl-4-(thiomethylcarboximidato)phenylalanine ethylester, m.p. 148°-149°. A further 1.15 g (3 mmoles, 12.5%) of product isrecovered from the first ethyl acetate extract.

D. D,L-4-(Imidazol-2-yl)phenylalanine dihydrochloride hydrate

Starting with 6.1 g (16 mmoles) ofN-acetyl-α-ethoxycarbonyl-4-(thiomethylcarboximidato)phenylalanine ethylester and following the procedure of step B of Example 16, there isobtained 1.65 g (5.1 mmoles, 32%) of D,L-4-(imidazol-2-yl) phenylalaninedihydrochloride hydrate, m.p. 120°-140° (dec.).

EXAMPLE 21 D,L-4-(4,5-dihydroimidazol-2-yl)phenylalanine dihydrochloride

Starting with 5.0 g (13.1 mmoles) ofN-acetyl-α-ethoxycarbonyl-4-(thiomethylcarboximidato)phenylalanine ethylester (from step C of Example 20) and following the proceduure ofExample 17, there is obtained 2.45 g (8 mmoles, 61%) ofD,L-4-(4,5-dihydroimidazol-2-yl)phenylalanine dihydrochloride, m.p.240°-245° (dec.).

EXAMPLE 22 D,L-3-(Imidazol-2-yl)phenylalanine dihydrochloride hydrate

Substituting 19.6 g (100 mmoles) of 3-cyanobenzyl bromide for4-cyanobenzylbromide and following the procedure of steps A, B and C ofExample 20 and step B of Example 16, there is obtained 7.08 g (22mmoles, 22%) of ,L-3-(imidazol-2-yl)phenylalanine dihydrochloridehydrate, m.p. 250-255°.

EXAMPLE 23 D,L-3-(2,3-Dihydro-1H-indol-5-yl)-α-methylalanine A.1-Benzoyl-5-chloromethyl-2,3dihydro-1H-indole

1-Benzoyl-2,3-dihydro-1H-indole (Beilstein, 20, 257) (5.58 g, 25 mmole)is dissolved in 50 ml of glacial acetic acid, then 56 ml (ca 70 mmoles)of 40% formaldehyde are added, and dry hydrogen chloride passed into thesolution which is maintained at 70° for 3 hours. The solution isevaporated, and the residue dissolved in benzene, and again evaporatedto dryness to give 6.53 g of crude product. This residue is treated withcarbon tetrachloride-hexane to give 4.05 g (60%) of1-benzoyl-5-chloromethyl-2,3-dihydro-1H-indole, m.p. 107.5 - 110.0°.

D,L-3-(2,3-dihydro-1H-indol-5-yl)-α-methylalanine

1-Benzoyl-5-chloromethyl-2,3-dihydro-1-H-indole (14.85 g, 54.65 mmoles)and 6.95 g (54.65 mmoles) of ethyl 2-isocyanopropionate are dissolved in100 ml of dimethylformamide. Then 7.72 g (60 mmole) of potassiumtertiarybutoxide is added in three equal portions during a period of tenminutes. The internal temperature rises from 16° to 23° even withexternal cooling. The mixture is stirred for 0.5 hour, diluted withwater, and extracted with diethyl ether. The combined etheral extractsare washed, dried over magnesium sulfate, and evaporated to give 13.3 g(67.2%) ofD,L-3-(1-benzoyl-2,3-dihydro-1H-indole-5-yl)-2-isocyano-2-methylpropionicacid ethyl ester, as a light red-brown oil which is suitable for thefollowing procedure.

D,L-3-(1-benzoyl-2,3-dihydro-1H-indol-5-yl)-2-isocyano-2-methylpropionicacid ethyl ester (13.3 g, 36.4 mmoles) is treated with 100 g of ice,then 250 ml of concentrated hydrochloric acid is added, and the solutionrefluxed for a period of six hours. The mixture is refrigerated, and thesolids collected to give 3.93 g of benzoic acid. The filtrate isevaporated to a small volume, then the pH adjusted to 10 with 15%ammonium hydroxide, the solution evaporated, and the residue dissolvedin water. The aqueous solution is passed through an ion exchange columnpacked with Dowex 50W-X8 cation exchange resin and the product elutedwith 1N aqueous ammonia solution. The resulting solids after evaporationof the aqueous ammonia solution are triturated with ethanol to give 4.26g (57.7%) of D,L-3-(2,3-dihydro-1H-indol-5-yl)-α-methylalanine, m.p.264°-268° (dec).

EXAMPLE 24 D,L-α-Methyl-3-(1H-2-oxindol-5-yl)alanine A. D,L-3-(1-Benzoyl-2,3-dihydro-1H-indol-5-yl)-2-isocyano 2-methylpropionic acidmethyl ester

Methyl 2-isocyanopropionate (9.4 g, 83 mmoles) is added with cooling toa cold solution of 4.5 g (83 mmoles) of sodium methylate in 50 ofdimethylformamide. The solution is added during the course of 10 minutesto a solution of 14.9 g (55 mmole) of1-benzoyl-5-chloromethyl-2,3-dihydro-1H-indole (from step A of Example23) in 50 ml of dimethylformamide maintained at 0°-12°. The mixture isstirred for 0.5 hour, then poured into 1000 ml of ice water, the solidscollected, and dried to give 16.1 g (84%) of crude product. The crudeproduct is crystallized from ethyl acetate to giveD,L-3-(1-benzoyl-2,3-dihydro-1H-indol-5-yl)-2-isocyano-2-methylpropionicacid methyl ester, m.p. 148°-150°.

B. D,L-3-(1-Benzoyl-2,3-dihydro-1H-indol-5-yl)-N-formyl-α-methylalaninemethyl ester

D,L-3-(1-benzoyl-2,3-dihydro-1H-indol-5-yl)-2-isocyano-2-methylpropionic acid methyl ester (348 mg, 1mmole) is stirred for 0.5 hourunder N₂ in a solution of 11 ml of ethyl acetate containing three dropsof concentrated hydrochloride acid. The mixture is extracted with water,the ethyl acetate layer dried over magnesium sulfate, filtered, andevaporated to give 365 mg of crude product. The residue is crystallizedfrom a mixture of chloroform and ethyl acetate to give 291 mg (79.4%) ofD,L-3-(1-benzoyl-2,3-dihydro-1H-indol-5-yl)-N-formyl-α-methylalaninemethyl ester, m.p. 163°-166°.

C. D,L-3-(1-benzoyl-1H-indol-5-yl)-N-formyl-α-methylalanine methyl ester

D,L-3-(1-benzoyl-1N-indol-5-yl)-N-formyl-α-methylalanine methyl ester(8.1 g, 22 mmoles) is dissolved in 400 ml of chloroform, the solutioncooled to 40°, then 7.5 g (33 mmoles) of2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) added and the solutionis refluxed for three hours under N₂. The solution is cooled, dilutedwith 200 ml of chloroform, the chloroform solution extracted with 3 × 10ml of 5% sodium carbonate solution, the combined chloroform extractswashed with water, dried over magnesium sulfate, filtered and evaporatedto give a solid residue. The solid is crystallized from ethylacetate-diethyl ether to give 6.24 g (77.8%) ofD,L-3-(1-benzoyl-1H-indol-5-yl)-N-formyl-α-methylalanine methyl ester,m.p. 111°-115°.

D. D,L-3-(1-benzoyl-3-bromo-1H-indol-5-yl)-N-formyl-α-methylalaninemethyl ester

D,L-3-(1-benzoyl-1H-indol-5-yl)-N-formyl-α-methylalanine methyl ester(6.56 g, 18 mmoles) is dissolved in 55 ml of chloroform,, then 2.96 g(18.5 mmoles) of bromine in 50 ml of chloroform are added during aperiod of 10 minutes accompanied by a small rise in internaltemperature. The solution is left 15 minutes at room temperature, thenextracted with water, the combined chloroform extracts dried overmagnesium sulfate, and evaporated to give 9 g of solids. The solids aretriturated with about 100 ml of diethyl ether to give 7.37 g (92.4%) ofD,L-3-(1-benzoyl-3-bromo-1H-indol-5-yl)-N-formyl-α-methylalanine methylester, m.p. 183°-185°.

E. D,L-α-methyl-3-(1H-2-oxindol-5-yl)-alanine

D,L-3-(1-benzoyl-3-bromo-1N-indol-5-yl)-N-formyl-α-methylalanine methylester (6.21 g, 14 mmoles) is suspended in a mixture of 200 ml ofmethanol, 40 ml of concentrated hydrochloric acid, and 10 ml of waterand heated for 3 hours at 80°. The methanol is removed in vacuo, 120 mlof concentrated hydrochloric acid added and the solution heated for afurther 8.5 hours. The solution is evaporated in vacuo. The residue isdissolved in water and evaporated several times. Ammonium hydroxide isadded, the solution evaporated, and the residue triturated with ethanolto give 4.7 g of solids. The solids are crystallized from ethanolwaterto give 1.1 g (28.5%) of D,L-α-methyl-3-(1H-2-oxindol-5-yl)alanine, m.p.300° (dec).

EXAMPLE 25 D,L-3-(1H-indol-5-yl)-α-methylalanine

D,L-3-(1-benzoyl-1H-indol-5-yl)-N-formyl-α-methylalanine methyl ester(3.2 g, 8.8 mmoles) (from step C of Example 24) is refluxed 6 hoursunder N₂ in 45 ml of methanol and 32 ml 2N sodium hydroxide solution.The methanol is removed in vacuo, 2N hydrochloric acid is added to thecooled basic solution until the pH is adjusted to 3.4 The solution isextracted with diethyl ether to remove benzoic acid. The aqueous acidsolution is treated with ammonium hydroxide to give a pH of 10, themixture refrigerated, the solids collected, washed, and dried to give1.2 g (63%) of D,L-3-(1H-indol-5-yl)-α-methylalanine, m.p.283°-285°(dec).

EXAMPLE 26 D,L-3-(Benzimidazol-2-thione-5-yl)-2-methylalanine hydrate A.D,L-N-Formyl-α-methyl-4-formylamino-3-nitrophenylalanine methyl ester

D,L-N-Formyl-α-methyl-4-aminophenylalanine methyl ester, 91.4 g, 387mmoles, (from step C of Example 11) is added to 500 ml of benzene.Formic-acetic anhydride (50% excess) is added and the mixture refluxedfor 30 minutes. The resulting solution is washed with 1N aqueous sodiumcarbonate until the washes remain basic. The benzene solution is thendried (MgSO₄) and evaporated to give 80.3 g ofD,L-N-formyl-α-methyl-4-formylaminophenylalanine methyl ester as an oil.Nitration as in step B of Example 11 of this oil affords 63.5 g ofD,L-N-formyl-α-methyl-4-formylamino-3-nitrophenylalanine methyl ester,m.p. 177°-179°.

B. D,L-N-Formyl-α-methyl-4-amino-3-nitrophenylalanine methyl ester

D,L-N-formyl-α-methyl-4-formylamino-3-nitrophenylalanine methyl ester(15 g, 48.5 mmoles) is treated according to the procedure of step A ofExample 9. There is obtained 13.6 g (100%) ofD,L-N-formyl-α-methyl-4-amino-3-nitrophenylalanine methyl ester, m.p.133°-136°.

C. D,L-3,4-Diamino-N-formyl-α-methylphenylalanine methyl ester

A mixture of 3.0 g (10.7 mmoles) ofD,L-N-formyl-α-methyl-4-amino-3-nitrophenylalanine methyl ester and 100ml of methanol is hydrogenated over 0.20 g of 10% pd on charcoal under18.2 kg of hydrogen pressure for 30 minutes. The reaction mixture isfiltered, the filtered solution evaporated to dryness, 50 ml of benzeneis added and re-evaporated and the residue triturated with 25 ml ofether. The resulting solid is filtered to yield 2.5 g (94%) ofD,L-3,4-diamino-N-formyl-α-methylphenylalanine methyl ester, m.p.118°-120°.

D. D,L-3-(Benzimidazol-2-thione-5-yl)-2-methylalanine hydrate

To a solution of 6 grams (24 mmoles) ofD,L-3,4-diamino-N-formyl-α-methylphenylalanine methyl ester in 100 ml ofmethanol is added 5.4 grams (72 mmoles) of carbon disulfide and 4.0 g(72 mmoles) of potassium hydroxide pellets dissolved in 15 ml of water.The reaction mixture is refluxed for 2 hours and then evaporated toremove the methanol. 50 ml of water are then added to the residuefollowed by 5 ml of acetic acid. The precipitate is filtered and washedwith water. The crudeD,L-3-(Benzimidazol-2-thione-5-yl)-N-formyl-α-methylalanine methyl esteris heated with 200 ml of 6N HCl for 3 hours on a steam bath. Thesolution is evaporated and the residue taken up in 50 ml of water. Thesolution is basified with ammonium hydroxide, evaporated to dryness andthen boiled in water. The product is filtered and dried at 100°. Yield,2.2 g (33%), m.p. 280° (dec.).

EXAMPLE 27 A. D,L-3-(2-Aminobenzimidazol-5-yl)-2-methylalaninedihydrochloride D,L-N-acetyl-3,4-diamino-α-methylphenylalanine methylester

A suspension of 10.0 g (34 mmoles) ofD,L-N-acetyl-4-amino-α-methyl-3-nitrophenylalanine methyl ester(prepared as in step A of Example 9) and 1.0 of 10% Pd on charcoal in300 ml of methanol is shaken under hydrogen at 18.2 kg pressure untilhydrogenation is complete (30 minutes). The reaction mixture isfiltered, evaporated to dryness, the residue slurried with 50 ml ethylacetate and again evaporated. The resulting solid is slurried well with100 ml of ether and filtered to yield 7.87 g (87%) ofD,L-N-acetyl-3,4-diamino-α-methylphenylalanine methyl ester, m.p.136°-139°.

B. D,L-3-(2-aminobenzimidazol-5-yl)-2-methylalanine dihydrochloride

To a mixture of 1.0 g (3.8 mmoles) ofD,L-N-acetyl-3,4-diamino-α-methylphenylalanine methyl ester and 30 ml ofwater is added 1.0 g (9.5 mmoles) of cyanogen bromide in two equalportions at 30 minute intervals. The reaction mixture is stirred for 1hour at 25° and then extracted with 2 × 50 ml of ethyl acetate, which isdiscarded. The aqueous phase is evaporated to dryness and the residuedissolved in 20 ml of concentrated hydrochloric acid. The resultingsolution is refluxed for one hour, cooled and the resulting precipitatefiltered, washed well with ethanol and ether to yield 0.64 g (55%) ofD,L-3-(2-aminobenzimidazol-5-yl)-2-methylalanine dihydrochloride, m.p.300°-305° (dec.).

EXAMPLE 28 D,L-2-Methyl-3-(benzoxazol-2-on-6-yl)alanine hydrochloride A.D,L-3-Hydroxy-4-nitro-α-methylphenylalanine hydrochloride

D,L-N-formyl-3-hydroxy-α-methyl-4-nitrophenylalanine methyl esterprepared as in step A of Example 7 (2.8 g, 10 mmoles) in concentratedhydrochloric acid (20 ml) is heated on a steam bath for 8 hours. Thereaction mixture is concentrated to a small volume and the solid isfiltered to yield 2.54 g (92%) ofD,L-3-hydroxy-4-nitro-α-methylphenylalanine hydrochloride, m.p.239°-243° (dec.).

B. D,L-3-Hydroxy-4-amino-α-methylphenylalanine dihydrochloride

D,L-3-Hydroxy-4-nitro-α-methylphenylalanine hydrochloride (2.8 g, 10mmoles) in a mixture of ethanol (25 ml) and 5% hydrochloric acid (25 ml)is reduced by hydrogen gas in a Parr hydrogenator over 5% palladium oncharcoal. The absorption of hydrogen is over within 5 minutes.Evaporation of the solvent under vacuum leaves 2.2 g (78%) ofD,L-3-hydroxy-4-amino-α-methylphenylalanine dihydrochloride as a whitesolid, m.p. 210° (dec.).

C. D,L-2-Methyl-3-benzoxazol-2-on-6-yl)alanine hydrochloride

D,L-3-Hydroxy-4-amino-α-methylphenylalanine dihydrochloride (0.92 g, 3.2mmoles) is dissolved in water (15 ml) and phosgene is bubbled throughthe solution, keeping the temperature between 50° and 60° for 20minutes. A white solid precipitates from the solution during thereaction. It is filtered and air-dried to yield 350 mg (40%) ofD,L-2-methyl-3-(benzoxazol-2-on-6-yl)alanine hydrochloride, m.p. 285°(dec.).

The filtrate contains D,L-3-hydroxy-4-amino-α-methylphenylalaninedihydrochloride which is recycled to yield an additional 454 mg of thetitle compound. The overall yield is 91%, m.p. 285° (dec.).

EXAMPLE 29 D,L-3-(2-Aminobenzothiazol-6-yl)-2-methylalaninedihydrochloride A.D,L-N-Acetyl-3-(2-aminobenzothiazol-6-yl)-2-methylalanine methyl ester

To a mixture of 5.0 g (20 mmoles) ofD,L-N-acetyl-4-amino-α-methylphenylalanine methyl ester (prepared as instep A of Example 5) and 3.56 g (44 mmoles) of sodium thiocyanate in 50ml of acetic acid, cooled to 10°, is added a solution of 3.52 g (22mmoles) of bromine in 10 ml of acetic acid over a 15 minute period. Thereaction mixture is then stirred at 25° for 2 hours and the inorganicsalts which precipitate are removed by filtration. The filtrate isevaporated to dryness and the residue partitioned between 150 ml ofwater and 150 ml of ethyl acetate.

The aqueous solution is basified with solid sodium hydroxide (pH>10) andextracted with 100 ml of ethyl acetate. During the extraction, crystalsbegin to separate from the organic layer which upon filtration yields2.58 g (8.4 mmoles, 42%) ofD,L-N-acetyl-3-(2-aminobenzothiazol-6-yl)-2-methylalanine methyl ester,m.p. 228°-229°.

B. D,L-3-(2-aminobenzothiazol-6-yl)-2-methylalanine dihydrochloride

A mixture of 2.58 g (8.4 mmoles) ofD,L-N-acetyl-3-(2-aminobenzothiazol-6-yl)-2-methylalanine methyl esterand 60 ml of concentrated hydrochloric acid is heated to reflux for 1.5hours, cooled in the refrigerator, and the precipitated solid filteredto yield 1.91 g (5.9 mmoles, 70%) ofD,L-3-(2-aminobenzothiazol-6-yl)-2-methylalanine dihydrochloride, m.p.315°-320° (dec.).

EXAMPLE 30 A. D,L-3(2-Aminobenzothiazol-6-yl)alanine dihydrochlorideD,L-N-Formyl-4-nitrophenylalanine methyl ester

Starting with 45 g (0.217 mole) of D,L-N-formylphenylalanine methylester [G. E. Hein, et al., J. Am. Chem. Soc., 84, 4487 (1962)] andcarrying out a nitration as in step B of Example 11, there is obtained42.0 g (77%) of D,L-N-formyl-4-nitrophenylalanine methyl ester, m.p.99°-100° of a sample recrystallized from ethanol.

B. D,L-3-(2-Aminobenzothiazol-6-yl)-N-formylalanine methyl ester

Starting with 9.3 g (42 mmoles) of D,L-4-amino-N-formylphenylalaninemethyl ester (prepared by catalytic hydrogenation of 10.6 g (42 mmoles)of D,L-N-formyl-4-nitrophenylalanine methyl ester in 100 ml of methanolover 1.0 g of 10% Pd on charcoal under 18.2 kg hydrogen pressure for 1hour, filtration and evaporation of the filtrate to dryness) andproceeding as in step A of Example 29, there is obtained 3.1 g (26%) ofD,L-3-(2-aminobenzothiazol-6-yl)-N-formyl alanine methyl ester, m.p.166°-169°.

C. D,L-3-(2-aminobenzothiazol-6-yl)alanine dihydrochloride

A mixture of 3.1 g (11.1 mmoles) ofD,L-3-(2-aminobenzothiazol-6-yl)-N-formylalanine methyl ester and 40 mlof concentrated hydrochloric acid is heated to reflux for 1.5 hours,cooled in an ice bath and the precipitate filtered and dried to yield3.0 g (87%) of D,L-3-(2-aminobenzothiazol-6-yl)-alanine dihydrochloride,m.p. 295°-300° (dec.).

EXAMPLE 31 D,L-2-Methyl-3-(2,1,3-benzothiadiazol-5-yl)-alaninehydrochloride

A solution of 2.9 gm (11 mmoles) ofN-acetyl-3,4-diamino-α-methylphenylalanine methyl ester (prepared as instep A of Example 27) and 5.0 ml of thionyl aniline in 120 ml ofpyridine is heated to reflux for 5 hours. The solution is evaporated todryness, treated with a mixture of water and methanol and evaporated,the solid washed with 50 ml of 1N hydrochloric acid and water and dried.The resulting solid is slurried with a small amount of ether andfiltered to yield 2.31 g ofD,L-N-acetyl-3-(2,1,3-benzothiadiazol-5-yl)-2-methylalanine methylester.

A mixture of 2.31 g (7.9 mmoles) ofN-acetyl-3-(2,1,3-benzothiadiazoly-5-yl)-2-methylalanine methyl esterand 50 ml of 12N hydrochloric acid is heated to reflux for 1 hour,evaporated to dryness, redissolved in water and re-evaporated todryness. The residue is slurried with isopropanol and filtered to yield1.7 g (57%) of 3-(2,1,3-benzothiadiazol-5-yl)-2-methylalaninehydrochloride, m.p. 272°-274° (dec.).

EXAMPLE 32D,L-3-(1,3-Dihydrobenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine2,2-dioxide hydrate

A mixture of 7.5 g (24 mmoles) ofD,L-3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-N-formyl-2-methylalanine2,2-dioxide methyl ester (prepared as in step A of Example 33) and 5 gof sodium hydroxide in 100 ml of water is heated to reflux under anatmosphere of nitrogen for 1 hour. The reaction mixture is then cooled,made acidic with 6N hydrochloric acid and sufficient concentratedammonium hydroxide is added to make it basic. The solution is evaporatedto dryness, redissolved in a minimum of water and the solution passedthrough an acid resin (Dowex 50WX8). The product is eluted from theresin with 1N ammonium hydroxide, which upon evaporation and triturationof the residue with ethanol, gives 5.05 g (73%) ofD,L-3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine-2,2-dioxidehydrate, m.p. 234°-236°.

EXAMPLE 33D,L-3-(1,3-Dihydrobenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine2,2-dioxide methyl ester hydrochloride A.D,L-3-(1,3-Dihydrobenzo-2,1,3-thiadiazol-5-yl)-N-formyl-2-methylalanine2,2-dioxide methyl ester

To 30 ml of refluxing diglyme is added 560 mg (5.8 mmoles) of sulfamidein 15 ml of diglyme, followed immediately by addition of 1.4 g (5.6mmoles) of D,L-3,4-diamino-N-formyl-α-methylphenylalanine methyl ester(prepared as in step C of Example 26). Refluxing is continued for 30minutes, the solvent is evaporated and the residue dissolved in ethylacetate. The ethyl acetate solution is washed with water and then with5% sodium bicarbonate solution. The bicarbonate solution is thenacidified with hydrochloric acid, extracted with ethyl acetate, theorganic extracts dried and evaporated. Trituration with chloroform ofthe residue gives the crystalline product, 0.70 g (40%), m.p. 175°-178°.

B. D,L-3-(1,3-Dihydrobenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine2,2-dioxide methyl ester hydrochloride

To a solution of 2.0 g (6.4 mmoles) ofD,L-3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-N-formyl-2-methylalanine2,2-dioxide methyl ester in 100 ml of methanol is added 5 drops ofconcentrated hydrochloric acid and the solution left at 25°. Theaddition of acid is repeated every two days over a period of two weeksafter which time the solvent is evaporated and the residue is refluxedin 50 ml of toluene for 20 hours to remove residual methanol. Filtrationand drying yields 1.76 g (85%) ofD,L-3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine2,2-dioxide methyl ester hydrochloride, m.p. broad 145°-165° (dec.).

EXAMPLE 34 D,L-3-(1,3-Dihydrobenzo-2,1,3-thiadiazol-5-yl)-alanine5,5-dioxide hydrate A. D,L-4-Formamido-N-formylphenylalanine methylester

Starting with 42 g (0.167 moles) of D,L-N-formyl-4-nitrophenylalaninemethyl ester (prepared as in step A of Example 30) and hydrogenating asin step C of Example 11 and formylating as in step A of Example 26,there is obtained 19.8 g (47%) of D,L-4-formamido-N-formylphenylalaninemethyl ester, m.p. 105°-107°.

B. D,L-4-Formamido-N-formyl-3-nitrophenylalanine methyl ester

Starting with 18.0 g (72 mmoles) of D,L-4-formamidoN-formylphenylalanine methyl ester and carrying out a nitrationaccording to step A of Example 26, there is obtained 18.0 g (85%) ofD,L-4-formamido-N-formyl-3-nitrophenylalanine methyl ester, m.p.140°-141° of a sample recrystallized from methanol.

C. D,L-4-Amino-N-formyl-3-nitrophenylalanine methyl ester

Starting with 13.0 gm (44 mmoles) ofD,L-4-formamido-N-formyl-3-nitrophenylalanine methyl ester and carryingout a selective hydrolysis as in step A of Example 9, there is obtained9.8 g (83%) of D,L-4-amino-N-formyl-3-nitrophenylalanine methyl ester,m.p. 160°-163°.

D. D,L-3-(1,3-Dihydrobenzo-2,1,3-thiadiazol-5-yl)-N-formyl alanine2,2-dioxide methyl ester

Starting with 9.7 g (36 mmoles) ofD,L-4-amino-N-formyl-3-nitrophenylalanine methyl ester, and followingthe procedures of step C of Example 26, and step A of Example 33 thereis obtained 4.0 g (37%) ofD,L-3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-N-formylalanine2,2-dioxide methyl ester, a sample of which when recrystallized fromwater, has m.p. 182°-185°.

E. D,L-3-(1,3-Dihydrobenzo-2,1,3-thiadiazol-5-yl)alanine 2,2-dioxidehydrate

Starting with 4.8 g (16 mmoles) ofD,L-3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-N-formylalanine dioxidemethyl ester and following the procedure of Example 32, there isobtained 3.72 g (84%) ofD,L-3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-alanine 2,2-dioxidehydrate, m.p. 195°-225° (dec.).

Example 35D,L-3-(1,3-dihydro-1,3-dimethylbenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine2,2-dioxide hydrate A.D,L-3-(1,3-dihydro-1,3-dimethylbenzo-2,1,3-thiadiazol-5-yl)-N-formyl-2-methylalanine2,2-dioxide methyl ester

To a solution of 1.9 g (6.1 mmoles) ofD,L-3-(1,3-dihydrobenzo-2,1,3-thiadiazol-5-yl)-N-formyl-2-methyl alanine2,2-dioxide methyl ester (prepared as in step A of Example 33) in 50 mlof methanol, is added in portions a solution of 4 g (95 mmoles) ofdiazomethane in 200 ml of ether. The solvents are evaporated, theresidue dissolved in 150 ml of ethyl acetate, the organic solutionwashed with 5% sodium bicarbonate solution, water, dried and evaporated.Recrystallization of the residue from ethanol gives 1.2 g (58%) ofD,L-3-(1,3-dihydro-1,3-dimethylbenzo-2,1,3-thiadiazol-5-yl)-N-formyl-2-methylalanine 2,2-dioxide methyl ester, m.p. 167°-168°.

B.D,L-3-(1,3-dihydro-1,3-dimethylbenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine2,2-dioxide hydrate

A mixture of 1.0 g (2.9 mmoles) ofD,L-3-(1,3-dihydro-1,3-dimethylbenzo-2,1,3-thiadiazol-5-yl)-N-formyl-2-methylalanine 2,2-dioxide methyl ester, 0.50 g of sodium hydroxide and 6 ml ofwater is heated on the steam bath for 45 minutes. The reaction iscooled, acidified with 3N hydrochloric acid, rebasified withconcentrated ammonium hydroxide and evaporated to dryness. Threesuccessive portions of 25 ml of water are then evaporated from theresidue and 25 ml of water added and the insoluble solid filtered togive 0.85 g (92%) ofD,L-3-(1,3-dihydro-1,3-dimethylbenzo-2,1,3-thiadiazol-5-yl)-2-methylalanine2,2-dioxide hydrate, m.p. 250°-252° (dec.).

EXAMPLE 36 D,L-α-Methyl-3-[4-methyl-2(1H)-oxoquinolin-6-yl]alanine A.D,L-N-acetyl-4-(3-oxobutanamido)-α-methylphenylalanine methyl ester

N-acetyl-4-amino-α-methylphenylalanine methyl ester (5.01 g, 20 mmole),prepared as in step A of Example 5, is suspended in 200 ml of drybenzene, then warmed 20 minutes on the steam bath with 8.72 g (30mmoles) of 6-keto-2,2,4-trimethyl-1,3-dioxane (diketene acetone adduct)until solution results. The solution is heated on the steam bath for afurther hour until solids appear in the solution. The mixture isevaporated to dryness in vacuo, the residue triturated with diethylether, and the solids collected to yield 6.53 g (97.3%) ofD,L-N-acetyl-4-(3-oxobutanamido)-α-methylphenylalanine methyl ester,m.p. 183°-185°.

B. D,L-N-Acetyl-α-methyl -3-[4-methyl-2-(1H)-oxoquinolin-6-yl]alanine

D,L-N-acetyl-4-(3-oxobutanamido-α-methylphenylalanine methyl ester (6.53g, 19.5 mmoles) is added portionwise to 15 ml of concentrated sulfuricacid and the solution heated slowly to 100° during 38 minutes. Thesolution is cooled to 60° and slowly poured into 400 ml of ice-water,the solids collected, and dried to give 4.1 g (69.7%) of crudeD,L-N-acetyl-α-methyl-3 [4-methyl-2(1H)-oxoquinolin-6-yl]alanine, m.p.275°-278° (with gassing). The product is purified by solution in dilutesodium bicarbonate and extraction of the solution with ethyl acetate.The bicarbonate solution is acidified, the solids collected and dried togive 3 g (51%) of pureD,L-N-acetyl-α-methyl-3-[4-methyl-2(1H)oxoquinolin-6-yl]alanine, m.p.284°-287° (gassing).

C. D,L-α-Methyl-3-[4-methyl-2(1H)-oxoquinolin-6-yl]alanine

D,L-N-acetyl-α-methyl-3-[4-methyl-2(1H)-oxoquniolin-6-yl]alanine (3.02g, 10 mmoles) is refluxed for 5 hours in 60 ml of concentratedhydrochloric acid and the solvent is removed in vacuo. The crude residueis dissolved in distilled water, the solution treated with ammoniumhydroxide to give a pH of 10, and the solvent is removed in vacuo. Thesolid is triturated with distilled water to give 2.47 g (90.5%) ofD,L-α-methyl-3-[4-methyl-2(1H)-oxoquinolin-6-yl]alanine, m.p. 259°-263°(dec.).

EXAMPLE 37 D,L-3-[4-Methyl-2(1H)-oxoquinolin-6-yl]alanine A.D,L-N-acetyl-4-aminophenylalanine methyl ester (5.91 g, 25 mmoles)[Chem. Abst., 54, 22673b, (1960)] is warmed for 25 minutes on a steambath with 10.9 g (37.5 mmoles) of 6-keto-2,2,4-trimethyl-1,3-dioxene in200 ml of benzene (diketene acetone adduct), the crude product isolatedand purified as in step A of Example 36 to give 8.0 g (99%) ofD,L-N-acetyl-4-(3-oxobutanamido)phenylalanine methyl ester, m.p.137.5°-139.0°. B. D,L-N-Acetyl-3-[4-methyl-2(1H)-oxoquinolin-6-yl]alanine

A mixture of 8 g (25 mmole) ofD,L-N-acetyl-4-(3-oxobutanamido)phenylalanine methyl ester and 20 ml ofconcentrated sulfuric acid is heated for 93 minutes at 70°-90° and theproduct isolated as in step B of Example 36 to give 6.57 g (91.2%) ofD,L-N-acetyl-3-[4-methyl-2-(1H)-oxoquinolin-6-yl]-alanine which is ofsuitable purity for hydrolysis.

C. D,L-3-[4-methyl-2-(1H)-oxoquinolin-6-yl]alanine hydrate

D,L-N-acetyl-3-[4-methyl-2(1H)-oxoquinolin-6-yl]alanine (5.8 g, 20mmoles) is refluxed for 6 hours in 105 ml of concentrated hydrochloricacid. Working the reaction up according to the procedure of step C ofExample 36 gives 4.1 g (82.8%) ofD,L-3-[4--methyl-2(1H)oxoquinolin-6yl]alanine hydrate, m.p. 247°-249°(gassing).

EXAMPLE 38 D,L-2Methyl-3-(quinoxalin-6-yl)alanine dihydrochloride A.D,L-N-Formyl-2-methyl-3-(quinoxalin-6-yl)alanine methyl ester

A mixture of 10.0 g (35.6 mmoles) ofD,L-4-amino-N-formyl-α-methyl-3-nitrophenylalanine methyl ester(prepared as in step B of Example 26) and 300 ml of methanol ishydrogenated over 1.0 g of 10% Pd on charcoal under 18.1 kg of hydrogenpressure for 1 hour. The reaction mixture is filtered and the filtrateevaporated to dryness. The residue is dissolved in 70 ml of hot waterand to this solution is added a solution of 7.0 ml of 40% aqueousglyoxal (50 mmoles) and 8.0 g (77 mmoles) of sodium bisulfite in 50 mlof water. The resulting solution is heated on a steam bath for 25minutes, cooled and basified with sodium carbonate. Filtration anddrying of the resulting precipitate yields 7.9 g (81%) ofD,L-N-formyl-2-methyl-3-(quinoaxalin-6-yl)alanine methyl ester, m.p.167°-168°.

B. D,L-2-Methyl-3-(quinoxalin-6-yl)alanine dihydrochloride

A mixture of 7.3 g (26.8 mmoles) ofD,L-N-formyl-2-methyl-3-(quinoxalin-6-yl)alanine methyl ester and 70 mlof concentrated hydrochloric acid is heated to reflux for 1 hour. Thesolution is then evaporated to dryness, 50 ml of water added and againevaporated to dryness. The residue is dissolved in 100 ml of water anddecolorized by treating with 1 g of charcoal at 60° for 1 hour. Themixture is filtered, the filtrate evaporated to dryness and the residueslurried with 50 ml of ethanol. Filtration of the resulting solid yields5.57 g (68%) of D,L-2-methyl-3-(quinoxalin-6-yl) alaninedihydrochloride, m.p. 235°-250° (dec.).

EXAMPLE 39 D,L-2-Methyl-3-(2-hydroxyquinoxalin-6-yl)alanine andD,L-2-methyl-3-(2-hydroxyquinoxalin-7-yl)alanine

A mixture of 5.0 g (17.8 mmoles) ofD,L-4-amino-N-formyl-α-methyl-3-nitrophenylalanine methyl ester(prepared as in step B of Example 26) and 250 ml of methanol ishydrogenated over 0.30 g of 10% Pd on charcoal under 18.1 kg of hydrogenpressure for 45 minutes. The reaction mixture is filtered and thefiltrate evaporated to dryness. The residue is dissolved in 50 ml ofwater and to this solution is added a solution of 4.1 g (39.4 mmoles) ofsodium bisulfite and 1.8 g (24 mmoles) of glyoxalic acid in 20 ml ofwater and the whole is heated on the steam bath for 15 minutes. Thereaction mixture is cooled and extracted once with 100 ml of ethylacetate to remove impurities, basified with 5.0 g of sodium carbonateand extracted with 3 × 100 ml of ethyl acetate. The ethyl acetateextract is washed with 25 ml of water, dried and evaporated. The residue(2.7 g) is added to 40 ml of concentrated hydrochloric acid and themixture heated to reflux for 1 hour. The solution is evaporated todryness and the residue decolorized by redissolving in 100 ml of waterand warming at 60° for 1 hour with 0.5 g of charcoal. After filtration,the solution is made basic with concentrated ammonium hydroxide andevaporated to dryness. The residue is dissolved in a mimimum of waterand this solution passed through a strong acid resin (50W-X8). Elutionwith 1N ammonium hydroxide and evaporation gives a solid which isslurried with 20 ml of ethanol and filtered to yield 1.21 g (28%) of amixture of D,L-2-methyl-3-(2-hydroxyquinoxalin-6-yl)alanine andD,L-2-methyl-3-(2-hydroxyquinoxalin-7-yl)alanine, m.p. 220°-225° (dec.).Nuclear magentic resonance spectroscopy indicates the two isomers to bepresent in approximately equal amounts.

EXAMPLE 40 D,L-3-(2,3-Dihydroxyquinoxalin-6-yl)-2-methylalaninehemihydrochloride A. D,L-3-(2,3-Dihydroxyquinoxalin-6-yl)-N-formyl-2-methyl alanine methyl ester

A mixture of 5.0 g (20 mmoles) of D,L-3,4-diaminoN-formyl-α-methylphenylalanine methyl ester (prepared as in step C ofExample 26) and 60 ml of diethyloxalate is heated to reflux for 4 hoursand filtered hot. The solid product thus filtered is washed with 50 mlof ether to yield 4.9 g (80%) ofD,L-3-(2,3-dihydroxyquinoxalin-6-yl)-N-formyl-2-methylalanine methylester, m.p. 267°-269° (dec.).

B. D,L-3-(2,3-Dihydroxyquinoxalin-6-yl)-2-methylalaninehemihydrochloride

A mixture of 3.0 g (10 mmoles) ofD,L-3-(2,3-dihydroxyquinoxalin-6-yl)-N-formyl-2-methylalanine methylester and 60 ml of concentrated hydrochloric acid is heated to refluxfor 90 minutes. The reaction mixture is evaporated to dryness, theresidue taken up in 100 ml of water and decolorized by addition of 0.5 gcharcoal and warming on the steam bath for 15 minutes, the mixturefiltered and the filtrate evaporated to dryness. The residue is taken upin a minimum of warm water (about 10 ml ) and upon cooling the productcrystallizes. Filtration and drying yield 1.4 g (47%) ofD,L-3-(2,3-dihydroxyquinoxalin-6-yl)-2-methylalanine hemihydrochloride,m.p. 280°-285° (dec.).

EXAMPLE 41 D,L-3-(Quinoxalin-6-yl)alanine dihydrochloride A.D,L-4-Acetamido-N-acetylphenylalanine methyl ester

A solution of 89.5 g (0.38 mole) of D,L-N-acetyl-4-aminophenylalaninemethyl ester [Chem. Abst., 54, 22673b (1960)] in 680 ml of benzene and100 ml of acetic anhydride is heated on the steam bath for 15 minutesand then left at 25° for 16 hours. The crystallized solid is filtered,washed with 200 ml of ether and air dried to yield 98.5 g (93%) ofD,L-4-acetamido-N-acetylphenylalanine methyl ester, m.p. 173°-175°.

B. D,L-4-Acetamido-N-acetyl-3-nitrophenylalanine methyl ester

To 250 ml of 90% nitric acid cooled to -15° is added 98.5 g (0.35 mole)of D,L-4-acetamido-N-acetylphenylalanine methyl ester with stirring overa period of 20 minutes. The reaction mixture is stirred at -15° to -10°for 1.5 hours and then poured into 2 liters of ice cold saturated sodiumbicarbonate solution. More solid sodium bicarbonate is added, asnecessary, in order to make the solution weakly basic. After storing themixture in the refrigerator overnight the resulting crystals arefiltered, washed with water and dried to yield 98.2 g (86%) ofD,L-4-acetamido-N-acetyl-3-nitro-phenylalanine methyl ester, m.p.123°-125°.

C. D,L-N-Acetyl-4-amino-3-nitrophenylalanine methyl ester

A mixture of 86 g (0.266 mole) ofD,L-4-acetamido-N-acetyl-3-nitrophenylalanine methyl ester and 33.7 g(0.318 mole) of sodium carbonate in 2 liters of methanol is heated toreflux for 2 hours. The mixture is filtered hot to remove precipitatedsalts and the filtrate evaporated to leave an oil. To this oil is added300 ml of water and upon trituration a crystalline solid is obtainedwhich is filtered and dried to yield 36.3 g (49%) ofD,L-N-acetyl-4-amino-3-nitrophenylalanine methyl ester, m.p. 133°-134°.

D. D,L-3-(Quinoxalin-6-yl)alanine dihydrochloride

Proceeding as in steps A and B of Example 38 but starting withD,L-N-acetyl-4-amino-3-nitrophenylalanine methyl ester (10 g, 35.6mmoles) there is obtained 4.52 g (44%) of D,L-3-(quinoxalin-6-yl)alaninedihydrochloride, m.p. 185°-200° (dec.).

EXAMPLE 42 D,L-3-(2,3-Dihydroxyquinoxalin-6-yl)alanine hydrochloride

Procceding as in step A of Example 27, and steps A and B of Example 40but starting with 5 gm (17.8 mmoles) ofD,L-N-acetyl-4-amino-3-nitrophenylalanine methyl ester (prepared as instep C of Example 41) there is obtained 2.6 g (51%) ofD,L-3-(2,3-dihydroxyquinoxalin-6-yl)alanine hydrochloride, m.p.270°-280° (dec.).

EXAMPLE 43 D,L-3-(1,4-Benzoxazin-3-one-7-yl)-2-methylalaninehemihydrochloride

A mixture of D,L-3-carboxymethoxy-4-nitro-α-methyl phenylalaninehydrochloride (8.1g 28.2 mmoles), prepared as in Example 8, dissolved in20 ml concentrated hydrochloric acid, and stannous chloride dihydrate(40 g, 177 mmoles) also dissolved in 70 ml concentrated hydrochloricacid is heated on a steam bath for 2 hours. The mixture is poured into500 ml water and hydrogen sulfide gas is bubbled through the solution toremove tin salts. The precipitate is filtered off and the filtrate istaken to a small volume.D,L-3-(1,4-benzoxazin-3-one-7-yl)-2-methylalanine hemihydrochloridecrystallizes out and is filtered to yield 1.1 g (17%), m.p. 308° (dec.).

EXAMPLE 44 D,L-3-(1,4-Benzoxazin-3-one-7-yl)alanine hemihydrochloride A.D,L-N-acetyl-3-hydroxy-4-nitro-α-cyanophenyl alanine ethyl ester

A solution is formed by adding successively at 0° C. 3-hydroxy-4-nitrobenzyl chloride [S. B. Hanna, et al., J. Chem. Soc., 221 (1961)] (18.75g; 100 mmoles) and potassium t-butoxide (11.3g; 100 mmoles to 100 ml ofdimethyl formamide. In a separate flask, a mixture of ethyl acetamidocyanoacetate (18.75; 110 mmoles) and potassium t-butoxide (12.42 g; 110mmole) in 100 ml dimethyl formamide is stirred until a solution isobtained This solution is then added to the previous solution and theresulting mixture is kept at about 50° C. for several hours. It is thenleft at room temperature overnight.

Water (250 ml.) is added and the mixture is filtered removing a smallamount of organic polymeric material. The filtrate is extracted withethyl acetate; the organic layer is washed with water. The aqueous layeris then acidified with 5% hydrochloric acid and extracted with ethylacetate. After drying and evaporation of the ethyl acetate an oil isobtained that crystallizes to yield 22.8 g (71%) ofD,L-N-acetyl-3-hydroxy-4-nitro-α-cyano phenylalanine ethyl ester, m.p.154°-156°.

B. D,L-N-Acetyl-3-(carboethoxymethoxy)-4-nitro-α-cyanophenylalanineethyl ester

To D,L-N-acetyl-3-hydroxy-4-nitro-α-cyanophenylalanine ethyl ester (11g, 34.2 mmoles) in 150 ml acetone is added ethyl bromoacetate (5.8 g,34.5 mmoles), sodium iodide (5.1 g, 34.2 mmoles) and potassium carbonate(5.1 g, 36.8 mmoles). Reflux is maintained for 24 hours. Half of thevolume of acetone is evaporated off and the residue is poured onto water(500 ml). It is extracted with ether, the ether layer is washed withwater, and dried over magnesium sulfate. Concentration under vacuumleaves an oil that is crystallized from a mixture of petroleumether-chloroform (9:1 v/v) yielding 9.1 g (65%),D,L-N-acetyl-3-(carboethoxymethoxy)-4-nitro-α-cyanophenylalanine ethylester, m.p. 130°-133°.

C. D,L-3-(1,4-Benzoxazin-3-one-7-yl)alanine hemihydrochloride

D,L-N-acetyl-3-carboethoxymethoxy-4-nitro-α-cyanophenylalanine ethylester (8.6 g, 21.1 mmoles) in concentrated hydrochloric acid (100 ml) isrefluxed for five hours after which the solution is evaporated todryness. The residue is then dissolved in 50 ml concentratedhydrochloric acid, and stannous chloride dihydrate (28.5 g, 126 mmoles)in 50 ml concentrated hydrochloric acid is added. The resultingsolution, after being stirred at room temperature for 1 hour, is dilutedto about 400 ml with water. Hydrogen sulfide gas is bubbled into thesolution. The insoluble tin sulfides are filtered, and the solution isevaporated to dryness. The residue is taken up in 30 ml of 2%hydrochloric acid and crystallization gives 1.42 g (26%) ofD,L-3-(1,4-benzoxazin-3-one-7-yl)alanine hemihydrochloride, m.p. 285°(dec.).

EXAMPLE 45 D,L-3-(5-Hydroxy-4H-pyran-4-on-2-yl)-2-methylalanine

To a solution of 1.60 g (0.07 mole) of sodium in 210 ml of ethanol isadded 17.73 g (0.07 mole) of iodokojic acid [T. Yabuta, J. Chem. Soc.,575 (1924)] and 3 g (0.024 mole) ethyl 2-isocyanopropionate. To theabove solution, stirred under a nitrogen atmosphere, is added a solutionmade up of 1.60 g (0.07 mole) of sodium and 8.9 g (0.07 mole) of ethyl2-isocyanopropionate in 175 ml of ethanol over a period of 45 minutes.The reaction is stirred for a further 3 hours at room temperature,evaporated to dryness, the residue dissolved in water and extracted withethyl acetate. The aqueous phase is acidified with hydrochloric acid andagain extracted with ethyl acetate. The ethyl acetate is evaporated andthe brick red residue is refluxed in 200 ml of 3 N hydrochloric acid for15 hours, cooled and extracted with ethyl acetate, treated with charcoaland evaporated to dryness. The residue is redissolved in water, madebasic with ammonium hydroxide and evaporated to dryness. Upon additionof 25 ml of water, the product is obtained as a light yellow solid whichis filtered and dried. Yield 2.26 g (15%) m.p. 239°-241°.

EXAMPLE 46 D,L-3-(2-Hydroxy-4-pyridyl)-2-methylalanine

A solution of 20 g of crude 4-bromomethyl-2-fluoropyridine [P. T.Sullivan, et al., J. Med. Chem., 14, 211 (1971)], which containsapproximately 13 g (73 mmoles) of pure material in 100 ml ofdimethylformamide is cooled in an ice bath. To this solution is added acold solution of 11.3 g (100 mmoles) of methyl 2-isocyanopropionate and11.2 g (100 mmoles) of potassium t-butoxide in 75 ml of dimethylformamide. The temperature is allowed to rise to 25° and the reaction isstirred for one hour at 25° after which it is poured into one liter ofice water. The aqueous mixture is extracted with 3 × 200 ml of etherwhich is backwashed with 2 × 100 ml of water. The ether extracts aredried and evaporated to leave 24 g of a thick oil. To this oil is addedwith cooling and stirring 100 ml of concentrated hydrochloric acid. Themixture is then refluxed for 1 hour, evaporated to dryness and 100 ml ofwater again evaporated from the residue. The residue is finallydissolved in 200 ml of water and extracted with 2 × 100 ml of ethylacetate. From the organic extract there is recovered 4.1 g of4-dibromomethyl-2-hydroxypyridine, m.p. 159°-160°, resulting from thehydrolysis of 4-dibromomethyl-2-fluoropyridine present as an impurity inthe starting material.

The aqueous fraction is warmed to 80° with 1 g of charcoal for 30minutes, filtered, evaporated and the residue taken up in 50 ml ofwater, basified with concentrated ammonium hydroxide, and evaporated.The residue is treated with 10 ml of water, cooled and filtered to give2.2 g (11.2 mmoles, 15.5%) ofD,L-3-(2-hydroxy-4-pyridyl)-2-methylalanine, m.p. 315°-316° (dec.).

EXAMPLE 47 D,L-3-Cyano-α-methyltyrosine methyl ester hydrochloride A.3-(Diacetoxymethyl)-4-acetoxybenzyl chloride

3-Formyl-4-hydroxy benzyl chloride (675 g., 3.96 moles) in 3.5 liters ofacetic anhydride is refluxed for 24 hours. The reaction mixture isevaporated to dryness, triturated with a minimum amount of ether andfiltered to yield 987 g. (79%) of 3-(diacetoxymethyl)-4-acetoxybenzylchloride, m.p. 93°-95°.

B. 3-(Diacetoxymethyl)-4-acetoxybenzyl iodide

3-(Diacetoxymethyl)-4-acetoxybenzyl chloride (987 g., 3.14 mole) andsodium iodide (494 g., 3.29 moles) in 3.5 liters acetone are refluxedfor 6 hours. The reaction mixture is filtered, the filtrate isevaporated to dryness, triturated in ether and filtered to yield 1,162 g(91%) of 3-(diacetoxymethyl)-4-acetoxybenzyl iodide, m.p. 117°-120° C.

C. D,L-3-Formyl-α-methyltyrosine methyl ester hydrochloride hydrate

The anion of methyl 2-isocyano propionate is prepared by adding at -50°C methyl 2-isocyanopropionate (167 ml., 1.5 moles) to a solution ofpotassium t-butoxide (165 g., 1.5 moles) in 700 ml dimethyl formamide.To a solution of 3-(diacetoxymethyl)-4-acetoxybenzyl iodide (500 g.,1.23 moles) in 1.5 liter DMF cooled to -10° C is added the freshlyprepared anion solution over a period of 20 minutes. Towards the end ofthis reaction, the temperature is about 5° and the mixture is stirred atroom temperature for 2 hours. It is then poured into cold water,extracted with ethyl acetate, washed with water, dried and evaporated todryness to yield methylD,L-2-methyl-2-isocyano-3-[3-diacetoxymethyl)-4-acetoxyphenyl]-2-propionate(430 g., 89%). This intermediate is dissolved in 2.2 liters of ethylacetate and 10 ml concentrated hydrochloride acid in 30 ml water isadded slowly. External cooling is necessary to maintain the temperatureat about 20°-25°. The mixture is then neutralized with sodiumbicarbonate, washed with water dried and evaporated to dryness to yieldD,L-N-formyl-α-methyl-3-diacetoxymethyl-4-acetoxyphenylalanine methylester (410 g., 91%). This derivative is dissolved in 2 liters ofmethanol, 150 ml concentrated hydrochloric acid is added and theresulting mixture is stirred at room temperature for 3 days. Thesolution is evaporated to dryness, triturated in ether and filtered. Thesolid is then treated with a minimum amount of hot isopropanol. It isthen cooled and filtered, washed with ether and air-dried to yieldD,L-3-formyl-α-methyltyrosine methyl ester hydrochloride monohydrate(151 g, 42% from 3-(diacetoxymethyl)- 4-acetoxybenzyl iodide), m.p.145°-150° C (dec.).

D. D,L-3-Cyano-N-formyl-α-methyltyrosine methyl ester

Refluxing D,L-3-formyl-α-methyltyrosine methyl ester hydrochloridehydrate (119 g, 0.41 moles) with hydroxylamine hydrochloride (54 g, 0.78moles) and sodium formate (95 g, 1.4 moles) in 1.2 liters of formic acidfor three hours affords 72 g (67%) ofD,L-3-cyano-N-formyl-α-methyltyrosine methyl ester.

E. D,L-3-Cyano-α-methyltyrosine methyl ester hydrochloride

A mixture of 40 ml of concentrated HCl and 3.68 g (15 mM) ofD,L-3-cyano-N-formyl-α-methyltyrosine methyl ester is refluxed for 1hour. After cooling, to room temperature, the crystals are filtered andwashed with diethyl ether to yield about 2.06 grams (54%) ofD,L-3-cyano-α-methyltyrosine methyl ester hydrochloride, m.p. 267°(dec.).

EXAMPLE 48 L-α-Methyl-4-(pyrrol-1-yl)phenylalanine A.L-α-Methylphenylalanine methyl ester hydrochloride methanol

To 210 ml of methanol is added 47 ml of thionyl chloride over a 30minute period. To this solution is added 98 g (0.50 mol) ofL-α-methylphenylalanine hydrate (F.W. Bollinger, J. Med. Chem., 14, 373(1971) with cooling. The reaction is then stirred and heated at 50° for16 hours, after which the mixture is evaporated to dryness. The residueis slurried with 500 ml of ether and the resulting solid filtered toyield 124 g. (approximately 100%) of L-α-methylphenylalanine methylester hydrochloride methanolate, m.p. 103°-104°.

B. L-N-Formyl-α-methylphenylalanine methyl ester

To a suspension of 124 g. (0.50 mole) of L-α-methylphenylalanine methylester hydrochloride methanolate in 65 ml of formic acid is added 41 g.(0.60 mole) of sodium formate with stirring and cooling in an ice bath.After 15 minutes, 82 ml. of formic acetic anhydride is added to thestirred and cooled mixture at 25° for 18 hours, after which a further 82ml of formic acetic anhydride is added and the reaction left for afurther 3 hours after which time it is complete. The insoluble salts areremoved by filtration and washed with 100 ml each of ether andchloroform. The washings are combined with the filtrate and the wholeevaporated to give a thick oil which is stirred with cold water (500ml.) for 1.5 hours. This mixture is then extracted with 3 × 500 ml ofchloroform and the combined chloroform extracts washed with 200 ml of 1Nhydrochloric acid, 200 ml water, 5% sodium bicarbonate until the aqueouswash remained basic and finally with 2 × 100 ml of water. After dryingof the chloroform solution, evaporation and trituration of the residuewith petroleum ether there is obtained a crystalline solid, which isrecovered by filtration to give 98.4 g (89%) ofL-N-formyl-α-methylphenylalanine methyl ester, m.p. 55°-58°.

C. L-N-Formyl-α-methyl-4-nitrophenylalanine methyl ester

To 250 ml of 90% nitric acid maintained between -15° and -10° is addedin portions over 0.5 hour 97.8 g (0.44 moles) ofL-N-formyl-α-methylphenylalanine methyl ester. The reaction ismaintained at this temperature for 1 hour longer then poured slowly in2000 ml of an ice-water slush containing 200 g of sodium bicarbonate.More sodium bicarbonate is added, if necessary, in order to bring the pHup to 7. The gummy product which precipitates becomes a granular solidwhen the mixture is stirred mechanically for 1 hour, and afterrecovering by filtration, washing with 500 ml. of water and drying,there is obtained 99.4 g. (84%) ofL-N-formyl-α-methyl-4-nitrophenylalanine methyl ester, m.p. 90°-95°.

D. L-4-Amino-N-formyl(α-methylphenylalanine methyl ester

Starting with 98.9 g. (0.35 mole) ofL-N-formyl-α-methyl-4-nitrophenylalanine and following the procedure ofpart C of Example 11, but omitting the final recrystallization, there isobtained 69.3 g (83.5%) of L-4-amino-N-formyl-α-methylphenylalaninemethyl ester, m.p. 70°-76°.

E. L-N-Formyl-α-methyl-4-(pyrrol-1-yl)phenylalanine

A mixture of 10 gm (42 mmoles) ofL-4-amino-N-formyl-α-methylphenylalanine methyl ester, 5.6 g (42 moles)of 2,5-dimethoxytetrahydrofuran, 50 g of Amberlite^(R) IRC 50 (H) resinand 250 ml of toluene is heated and stirred at reflux for 4 hours.Filtration to remove the resin and evaporation of the filtrate leaves asemi-solid residue of 8.9 g, which after slurrying with 25 ml of etherand recovering the insoluble product by filtration yields 6.15 g (51%)of L-N-formyl-α-methyl-4-(pyrrol-1-yl)phenylalanine methyl ester, m.p.106°-109°.

F. L-α-Methyl-4(pyrrol-1-yl)phenylalanine

A mixture of 12 g (42 mmoles) ofL-N-formyl-α-methyl-4-(pyrrol-1-yl)phenylalanine methyl ester, 48 ml of40% aqueous sodium hydroxide and 180 ml of methanol is heated to refluxfor 5 hours after which it is evaporated to dryness. The residue isdissolved in 300 ml. of water and sufficient 12N hydrochloric acid isadded to bring the pH to about 5, whereupon the product crystallizes. Itis recovered by filtration, washed with 50 ml each of water, ethanol andether and finally dried in vacuum at 50° for 18 hours to yield 8.3 g(81%) of L-α-methyl-4-(pyrrol-1-yl)phenylalanine, m.p. 294°-295°(dec.).

EXAMPLE 49 D-α-Methyl-4-(pyrrol-1-yl)phenylalanine

Starting with 18.7 gm (95 mmoles) of D-α-methylphenylalanine hydrate (F.W. Bollinger, J. Med. Chem. 14, 373 (1971) and following the proceduresof parts A, B C, D, E and F of Example 48 for the synthesis of theL-isomer, there is obtained 3.7 gm. (15.8% overall yield) ofD-α-methyl-4-(pyrrol-1-yl)phenylalanine, m.p. 297°-299°.

EXAMPLE 50 L-α-Methyl-4-(pyrrol-1yl)phenylalanine methyl esterhydrochloride

To a stirred suspension of 3 g (12.3 mmoles) ofL-α-methyl-4-(pyrrol-1-yl)phenylalanine (prepared as in Example 48) in200 ml of methanol is added dropwise, and with stirring, at 25° anetheral solution of diazomethane until the yellow color of diazomethaneis no longer dissipated, at which point a homogenous solution isobtained. The reaction mixture is then evaporated to leave 3 g of anoil. Two grams of this oil are dissolved 45 ml of warm hexane and uponcooling, there is obtained 1.2 g of the methyl ester as the free base,m.p. 40°-41°. This material is dissolved in 100 ml of ether and anexcess of hydrogen chloride gas is passed into the solution toprecipitate 1.3 g (54%) of L-α-methyl-4-(pyrrol-1-yl)phenylalaninemethyl ester hydrochloride, m.p. 200°-202°.

EXAMPLE 51 D,L-4-[2-(carboxy)pyrrol-1-yl]-2-methylphenylalaninedihydrate A.D,L-4-[2-(Carbomethoxy)pyrrol-1-yl]-N-formyl-α-methylphenylalaninemethyl ester

A mixture of 5.0 g (21 mmoles) ofD,L-4-amino-N-formyl-α-methylphenylalanine methyl ester (prepared as inPart C of Example 11 ) and 4.03 g (21 mmoles) of2-carbomethoxy-2,5-dimethoxytetrahydrofuran in 40 ml of acetic acid isheated on the steam bath for 1.5 hours, cooled and poured into 300 ml ofcold water. The aqueous mixture is extracted with 3 × 100 ml of ethylacetate and the combined organic extracts washed with 0.5N sodiumhydroxide until the aqueous washings remain basic, and finally withwater. After drying and evporating the organic layer, the residual oilis chromatographed on silica gel to give 4.0 g ofD,L-4-[2-(carbomethoxy)pyrrol-1-yl]-N-formyl-α-methylphenylalaninemethyl ester as an oil which is satisfactory for use in the nextreaction.

B. D,L-4-[2-(Carboxy)pyrrol-1-yl]-α-methylphenylalanine dihydrate

A mixture of 3.6 g (10.5 mmoles) ofD,L-4-[2-(carbomethoxy)pyrrol-1-yl]-N-formyl-α-methylphenylalaninemethyl ester and 12 ml of 40% aqueous sodium hydroxide in 45 ml ofmethanol is heated to reflux for 2.5 hours, cooled and evaporated todryness. The residue is redissolved in 30 ml of water and the solutionmade slightly acidic by addition of acetic acid. The resultingcrystalline precipitate is recovered by filtration, washed with 20 ml ofwater, 20 ml of methanol and 100 ml of ether and dried in vacuum at 50°to give 1.64 g. (48%) ofD,L-4-[2-(carboxy)pyrrol-1-yl]-α-methylphenylalanine dihydrate, m.p.304-306 (dec.).

EXAMPLE 52 D,L-α-Methyl-3-(pyrrol-1-yl)phenylalanine hydrochloride A.D,L-N-Formyl-α-methyl-3-nitrophenylalanine methyl ester

Methyl 2-isocyanopropionate (7.95 g, 70.2 mmoles) is added slowly to asuspension of sodium methoxide (20% excess) in 40 ml. of drydimethylformamide at -5°. The resultant solution is added slowly to asolution of 3-nitrobenzylchloride (10 g, 58.5 mmoles) in 40 ml ofdimethylformamide at -5°. After the addition is complete the reactionmixture is allowed to reach room temperature. The mixture is added withstirring to a mixture of ice and water and extracted with ethyl acetate.The ethyl acetate extracts are combined and stirred with a few ml ofconcentrated hydrochloric acid for 2 hours at room temperature. Theethyl acetate solution is rinsed with water, 5% sodium bicarbonate,water and dried. The solution is filtered and evaporated to yield 13.50g (87%) of D,L-N-formyl-3-nitrophenylalanine methyl ester, m.p.120°-122°.

B. D,L-3-Amino -N-formyl-α-methylphenylalanine methyl ester

D,L-N-formyl-α-methyl-3-nitrophenylalanine methyl ester (43.09 g, 0.162moles) suspended in 200 ml methanol is hydrogenated on a Parrhyrogenator using 2 g of 5% palladium on charcoal. The catalyst isfiltered off and the filtrate is evaporated to dryness to yield 37.8 g(98%) of D,L-3-amino-N-formyl-α-methylphenylalanine methyl ester as anoil which is sufficiently pure for use in the next step.

C. D,L-α-Methyl-3-(pyrrol-1-yl)phenylalanine hydrochloride

To D,L-3-amino-N-formyl-α-methylphenylalanine methyl ester (35.1g, 148.5mmoles) dissolved in 180 ml glacial acetic acid is added2,5-dimethoxytetrahydrofuran (21.5 g, 163 mmoles). The mixture is heatedon a steam bath for 30 minutes. It is then poured onto ice and water (2liters) and extracted 5 times with 200 ml of chloroform. The extractsare combined, washed twice with 5% aqueous sodium bicarbonate, once withwater and dried with magnesium sulfate. Evaporation to dryness leaves38.5 g of brown oil which is then absorbed on 500 g of silica gel andeluted with chloroform to yield 19.9 g (44%) ofD,L-α-methyl-3-(pyrrol-1-yl)phenylalanine methyl ester, m.p. 80°-83°.

The ester (6 g, 21 mmole) is dissolved in 80 ml methanol; 15 ml 40%sodium hydroxide is added and the resulting mixture is refluxed for 16hours. The reaction mixture is evaporated to dryness. The residue isdissolved in water and glacial acetic acid is added to adjust the pH to6. The fine light cream precipitate is filtered, rinsed with water andair dried. This solid is added to 30 ml of 6N hydrochloric acid, thesuspension is stirred at room temperature for 90 minutes. It is thenfiltered, washed with isopropanol, with ether and then air dried toyield 5.15 g of D,L-α-methyl-3-(pyrrol-1-yl)phenylalanine hydrochloride,m.p. 205°-207° (dec.).

EXAMPLE 53 D,L-4-(Pyrrol-1-yl)phenylalanine A.D,L-4-Amino-N-formylphenylalanine methyl ester

Using 1.0 g of 5% palladium on charcoal as catalyst, 52.7 g (0.21 moles)of D,L-N-formyl-4-nitrophenylalanine methyl ester (prepared as in part Aof Example 30) in 200 ml of methanol is reduced under 18.1 kg ofhydrogen pressure. The catalyst is filtered off and the filtrateevaporated to yield 44 gm (94%) of D,L-4-amino-N-formylphenylalaninemethyl as oil suitable for use in the next reaction.

B. N-Formyl-4-(pyrrol-1-yl)phenylalanine

Under a stream of nitrogen, 44 grams (0.2 moles) ofD,L-4-amino-N-formylphenylalanine methyl ester and 30.5 g (0.23 mole) of2,5-dimethoxytetrahydrofuran dissolved in 250 ml of acetic acid isheated on a steam bath for 0.5 hour. The reaction mixture is dilutedwith 600 ml of H₂ O and extracted with chloroform. Some NaCl is added tobreak up the emulsion. The chloroform layer is washed with H₂ O anddilute bicarbonate solution, dried over MgSO₄ and evaported. Theresidual oil is purified by chromatography over silica gel to yield 31.5g (57.5%) of D,L-N-formyl-4-(pyrrol-1-yl)phenylalanine methyl ester,m.p. 117°-118°.

C. D,L-4-(pyrrol-1-yl)phenylalanine

Under a gentle stream of nitrogen, a mixture of 5.4 g (20 mmole) ofD,L-N-formyl-4-(pyrrol-1-yl)phenylalanine methyl ester, 16 ml of 7N NaOHand 75 ml of methanol is refluxed for 3 hours. The methanol isevaporated off and the residue taken up in H₂ O. Dilute HCl is added toobtain an acidic mixture. Dilute NH₄ OH is then added to obtain a basicmixture. The solid is filtered and washed with H₂ O. The solid isrecrystallized from 700 ml of 2N NH₄ OH to yield 2.6 g (50%) ofD,L-4-(pyrrol-1-yl)phenylalanine, m.p. 288° (dec.).

EXAMPLE 54 D,L-α-Methyl-4-(pyrrol-1-yl)phenylalanine methyl ester

Diazomethane (34 mmole) in diethyl ether (Fieser & Fieser; Reagents forOrg. Syn. p. 192) is added in portions to a suspension of 2.0 g (8.2mole) of D,L-α-methyl-4-(pyrrol-1-yl)phenylalanine from part E ofExample 11 in 50 ml of methanol at 0°. A solution is obtained after 1hour of stirring at room temperature. Dilute acetic acid in diethylether is then added dropwise until the yellow color fades. The solutionis filtered and evaporated. The residual solid is recrystallized fromn-hexane., m.p. 93°-94°.

D,L-α-Methyl-3-[4-(pyrrol-1-yl)phenyl]alanine methyl ester (1.0 g) isdissolved in 25 ml of diethyl ether. Dry HCl gas is bubbled into thesolution. The crystalline product is filtered and dried at 100° to yield1.1 g (97%) of D,L-α-methyl-4-(pyrrol-1-yl)phenylalanine methyl esterhydrochloride, m.p. 207° (dec.)

EXAMPLE 55 D,L-3-Hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalanine hydrateA. D,L-N-Formyl-3-hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalanine methylester

Using 2 g. of 10% palladium on carbon as catalyst, 25 g (88 mmole) ofD,L-N-formyl-3-hydroxy-α-methyl-4-nitrophenylalanine methyl ester frompart A of Example 6 dissolved in 300 ml of methanol is reduced using aParr hydrogenator. The catalyst is filtered off and the filtrateevaporated to obtain 21.1 g (95%) of an oil which is of sufficientquality for the next step.

To a solution of 16.3 g (65 mmole) ofD,L-4-amino-N-formyl-3-hydroxy-α-methylphenylalanine methyl ester, asprepared above, in 100 ml of acetic acid is added in one portion 9 g (68mmole) of 2,5-dimethoxytetrahydrofuran. The solution is refluxed for 30minutes and then poured into ice and water. The aqueous mixture isextracted with ethyl acetate. The organic layer is washed with dilutesodium bicarbonate and water, dried over Na₂ SO₄, filtered andevaporated. The residue is purified on silica gel to yield 6.12 g (30%)of D,L-N-formyl-3-hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalanine methylester, m.p. 132°-135°.

B. D,L-3-Hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalanine hydrate

In a glass bomb is placed 20 ml of 40% NaOH, 50 ml of methanol and 5 g(16 mmole) ofD,L-N-formyl-3-hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalanine methylester. The sealed bomb is heated at 120° for 1 hour. The cooled solutionis evaporated and the residue redissolved in 50 ml of water. Thesolution is neutralized with acetic acid and the product is filtered,washed with water and dried in a vacuum oven at 50° for 18 hours toyield 4.0 g (87%) ofD,L-3-hydroxy-α-methyl-4-(pyrrol-1-yl)-phenylalanine hydrate, m.p. 315°(dec.)

EXAMPLE 56 D,L-3-Methoxy-α-methyl-4-(pyrrol-1-yl)phenylalanine oxalicacid salt

With magnetic stirring, a mixture of 3.5 g (26 mmole) of methyliodide, 2g (14 mmole) of potassium carbonate, 120 ml of acetone and 4.0 g (13mmole) of D,L-N-formyl-3-hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalaninemethyl ester (from part A of Example 55) is refluxed for 5 hours. Themixture is filtered and the filtrate evaporated. The residue isdissolved in ethyl acetate, washed with water, dried over Na₂ SO₄,filtered and evaporated to obtain 4.3 g (93%) of an oil which is ofsufficient purity for the next step.

A solution of 12 ml of 40% NaOH, 40 ml of methanol and 4.3 g (13 mmole)of D,L-N-formyl-3-methoxy-α-methyl-4-(pyrrol-1-yl)phenylalanine methylester prepared as above is refluxed for 3 hours with magnetic stirring.The solution is evaporated and the residue redissolved in 40 ml ofwater. The solution is neutralized with hydrochloric acid and theproduct is filtered, washed with water and dried in a vacuum oven at 50°for 18 hours to yield 3.27 g (92%) m.p. 230° (dec.).

The oxalic acid salt is prepared by magnetically stirring for 1 hour, amixture of 1.0 (11 mmole) of oxalic acid, 50 ml of methanol and 3.0 g(11 mmole) of D,L-3-methoxy-α-methyl-4-(pyrrol-1-yl)phenylalanineprepared above. Insoluble impurities are filtered off and the filtratetreated with charcoal. The solution is evaporated and the residue washedwith diethyl ether to remove excess oxalic acid to yield 3.15 g (78%) ofD,L-3-methoxy-α-methyl-4-(pyrrol-1-yl)phenylalanine oxalate, m.p. 188°(dec.)

EXAMPLE 57 D,L-α-Methyl 3-(pyrrol-1-yl)tyrosine oxalate monohydrate A.D,L-α-Methyl-3-nitrotyrosine methyl ester hydrochloride

A solution of 42.0 g (180 mmole) of D,L-α-methyl-3-nitrotyrosine[prepared as described by Saari, et al., J. Med Chem., 10, 1008 (1967)]in 200 ml of methanol saturated with dry hydrogen chloride is heated toreflux for 10 hours, evaporated to dryness and the residue slurried with200 ml of ether. The solid is recovered by filtration to give 50 g (97%)of D,L-α-methyl-3-nitrotyrosine methyl ester hydrochloride, m.p.,202°-203° (dec.).

B. D,L-N-Formyl-α-methyl-3-nitrotyrosine methyl ester

To a solution of 50 g of D,L-α-methyl-3-nitrotyrosine methyl esterhydrochloride in 200 ml of formic acid is added 100 ml of formic aceticanhydride, and the mixture stirred at 25° for 2 hours. A precipitate isfiltered off and the resulting solid (9.5 g) identified asD,L-N-formyl-α-methyl-3-nitrotyrosine. The filtrate is evaporated todryness and the residue slurried with 100 ml of water and filtered togive 37 g of crude product. This is suspended in 200 ml of water and themixture extracted with 3 × 200 ml of ethyl acetate. From the ethylacetate extracts there is obtained, after drying and evaporation, 30.8 g(78%) of D,L-N-formyl-α-methyl-3-nitrotyrosine methyl ester, m.p.129°-132°.

C. D,L-3-Amino-n-formyl-α-methyltyrosine methyl ester

To a solution of 20 g (71 mmole) ofD,L-N-formyl-α-methyl-3-nitrotyrosine methyl ester in 300 ml of methanolis added 2.0 g of 10% palladium on charcoal and the resulting mixturereduced under 18.1 kg of hydrogen pressure for 30 minutes. The reactionmixture is filtered and the filtrate evaporated to dryness. Thecrystalline residue is slurried with 25 ml of methanol and the solidrecovered by filtration to yield 15.5 g (86%) ofD,L-3-amino-N-formyl-α-methyltyrosine methyl ester, n.p. 197°-199°.

D. D,L-N-Formyl-α-methyl-3-(pyrrol-1-yl)tyrosine methyl ester

A solution of 15 g (60 mmole) of D,L-3-amino-N-formyl-α-methyltyrosinemethyl ester and 6.2 ml (66 mmole) of 2,5-dimethoxytetrahydrofuran in 80ml of acetic acid is heated to reflux for 30 minutes. The reactionmixture is then poured into 400 ml of ice and water which is thenextracted with 3 × 200 ml of ethyl acetate. The combined ethyl acetateextracts are washed with 1N sodium bicarbonate until the aqueous layerremains basic, dried and concentrated. The residue is purified bypassage through a column of silica gel. Elution with ethyl acetate gives7.3 g (40%) of crystalline D,L-N-formyl-α-methyl-3-(pyrrol-1-yl)tyrosinemethyl ester, m.p. 151°-152°.

E. D,L-α-Methyl-3-(pyrrol-1-yl)tyrosine oxalate monohydrate

A mixture of 2.0 g (6.6 mmole) ofD,L-N-formyl-α-methyl-3-(pyrrol-1-yl)tyrosine methyl ester, 8 ml of 40%aqueous sodium hydroxide and 30 ml of methanol is heated to reflux for 4hours. The solvent is evaporated and the residue dissolved in 50 ml ofwater, made acidic with concentration hydrochloric acid and then madeweakly basic (pH 9) with ammonium hydroxide. The solution is thenevaporated to dryness and the residue is stirred with 50 ml of water for30 minutes and the insoluble material recovered by filtration to give1.51 g of crude product. The crude material is added to 25 ml ofmethanol, followed by addition of 540 mg of oxalic acid. Insolubleimpurities are removed by filtration and the filtrate is evaporated todryness. From the residue, 50 ml of water is evaporated and the residuedried under vacuum at 50° for 5 hours to give 1.66 g (68%) ofD,L-α-methyl-3-(pyrrol-1-yl)tyrosine oxalate monohydrate, m.p.105°-115°.

EXAMPLE 58 D,L-4-Methoxy-α-methyl-3-(pyrrol-1-yl)phenylalanine oxalatemonohydrate A.D,L-N-Formyl-4-methoxy-α-methyl-3-(pyrrol-1-yl)phenylalanine methylester

A mixture of 3.5 g (11.6 mmole) ofD,L-N-formyl-α-methyl-3-(pyrrol-1-yl)tyrosine methyl ester (prepared asin part D of Example 57) 1.7 g of potassium carbonate and 3.0 g ofmethyl iodide in 120 ml of acetone is heated to reflux for 8 hours. Theacetone is removed by evaporation and the residue dissolved in 150 ml ofethyl acetate. The ethyl acetate solution is washed with 2 × 100 ml ofwater, dried and evaporated to yield 3.6 g ofD,L-N-formyl-4-methoxy-α-methyl-3-(pyrrol-1-yl)phenylalanine methylester as an oil which is suitable for use in the next reaction.

B. D,L-4-Methoxy-α-methyl-3-(pyrrol-1-yl)phenylalanine oxalatemonohydrate

The hydrolysis of 3.6 g (11.3 mmole) ofD,L-N-formyl-4-methoxy-α-methyl-3-(pyrrol-1-yl)phenylalanine methylester is carried out according to the procedure in Example 56 to give1.9 g of crude amino acid. This material is converted to the oxalate bythe procedure of Example 56 to yield 1.83 g (42%) ofD,L-4-methoxy-α-methyl-3-(pyrrol-1-yl)phenylalanine oxalate monohydrate,m.p. 100°-110°.

EXAMPLE 59 D,L-4-(Indol-1-yl)-α-methylphenylalanine hydrate A.p-(Indol-1-yl)benzoic acid

A mixture of 180 ml of 6N NaOH, 360 ml ethylene glycol and 39.3 g (180mmole) of 1-p-cyanophenylindole [Misbahul Ain Khan and J. B. Polya, J.Chem. Soc., 85 (1970)] is refluxed for 3 hours at 150°. The basicsolution is diluted with 450 ml of H₂ O and extracted with diethyl etherto remove neutrals. The aqueous solution is acidified with 200 ml of 6NHCl. The solid is filtered washed with hot water and dried in a vacuumoven at 50° to yield 45.8 g (95%) of p-(indol-1-yl)benzoic acid, m.p.224°-226°.

B. 1-(p-Hydroxymethyl)phenylindole

To a mechanically stirred suspension of 12.5 g (330 mmole) of LiAlH₄ in600 ml of diethyl ether is added dropwise 45.8 g (180 mmole) ofp-(indol-1-yl)benzoic acid dissolved in 458 ml of dry tetrahydrofuran.The reaction mixture is stirred at 0° for 2 hours and then decomposed bysequential addition of 12.5 ml H₂ O, 12.5 ml of 15% NaOH and 37.5 ml ofH₂ O. The salts are filtered and washed with diethyl ether. The filtrateis evaporated to dryness, redissolved in diethyl ether and washed withH₂ O 1N NaOH solution and H₂ O. The ether solution is dried over Na₂SO₄, filtered and evaporated. The oil is dried in a vacuum oven at 50°overnight. The oil crystallizes slowly over several days to yield 27.8 g(68%) of 1-(p-hydroxymethyl)phenylindole, m.p. 37°-39°.

C. D,L-N-Formyl-4-(indol-1-YL)-α-methylphenylalanine methyl ester

To a solution of 11.15 g (50 mmole) of 1-(p-hydroxymethyl)phenylindolein 250 ml of benzene is added in portions 11.9 g (57 mmole) of PCl₅. Themixture is stirred at about 10° for 15 minutes. Insolubles are filteredoff and the filtrate washed with 2 × 100 ml of ice water, dried over Na₂SO₄, filtered and evaporated to yield 14 g of an oil which is ofsufficient quality for the next step.

A solution of 14 g of p-(indol-1-yl)benzylchloride, prepared as above,dissolved in 75 ml of DMF is stirred magnetically at -45°. To thissolution is added over 5-10 minutes, an anion solution prepared by theaddition of 8.48 g (75 mmole) of methyl 2-isocyanopropionate to 4.05 g(75 mmole) of sodium methoxide contained in 75 ml of DMF at -45°. Thetemperature of the resultant mixture is permitted to gradually rise to-15°. Water (900 ml) is then added, not allowing the temperature toexceed 10°. The mixture is extracted with ethyl acetate which is thenevaporated. The residue is taken up in diethyl ether, washed with H₂ Odried over Na₂ SO₄, filtered and evaporated to yield 15.9 g of an oilwhich is hydrolyzed as such.

32.9 g. of crude methyl2-isocyano-3-[4-(indol-1-yl)phenyl]2-methylpropionate prepared as above,is dissolved in 300 ml of ethyl acetate at 5° and with magnetic stirringis added dropwise 2.5 ml of concentrated HCl. After stirring for 15minutes, the solution is diluted with H₂ O. The separated organic layeris dried over Na₂ SO₄, filtered and evaporated. The crude product ispurified on silica gel to yield 25 g. (66% overall). The product isrecrystallized from benzene to giveD,L-N-formyl-4-(indol-1-yl)phenylalanine methyl ester of m.p. 146°-148°.

D. D,L-4-(Indol-1-yl)-α- methylphenylalanine hydrate

A mixture of 25 ml of 3N NaOH solution, 100 ml of methanol, and 3.0 g (9mmole) of D,L-N-formyl-4-(indol-1-yl)-α-methylphenylalanine methyl esteris refluxed on a steam bath for 1.5 hours. The methanol is evaporatedoff and 50 ml of H₂ O added. The solution is then refluxed in an oilbath at 115° for 4 hours with a nitrogen atmosphere being maintainedthroughout hydrolysis. A solution of 27 ml of 3N HCl is added to thecooled solution followed by 10 ml of 1N sodium acetate solution to givea pH of 3.0. The solid is filtered, washed with some hot water and driedovernight in a vacuum oven at 60° to yield 2.59 g (88%) ofD,L-4-(indol-1-yl)-α-methylphenylalanine hydrate, m.p. 270°-273°.

EXAMPLE 60 D,L-4-(Carbazol-9-yl)-α-methylphenylalanine A.9-(p-Hydroxymethyl)phenylcarbazole

To a mechanically stirred suspension of 4.7 (124 mmole) of LiAlH₄ in 300ml of diethyl ether is added dropwise 18 g (62 mmole) of9-(p-carboxy)phenyl carbazole (C.A. Vol 34, p. 1658) dissolved in 120 mlof dry tetrahydrofuran. The reaction mixture is stirred at 5° for 1 hourand then decomposed by sequential addition of 4.7 ml of H₂ O, 4.7 ml of15% NaOH and 14.1 ml of H₂ O. The salts are filtered and washed withdiethyl ether. The filtrate is evaporated to dryness, redissolved indiethyl ether, washed with H₂ O, dried over Na₂ SO₄, filtered andevaporated to yield 15.1 g (88%) of 9-(p-hydroxymethyl) phenylcarbazole. A sample recrystallized from cyclohexane has m.p. 121°-122°.

B. P-(Carbazol-9-yl)benzylchloride

To a suspension of 8.19 (30 mmole) of 9-(p-hydroxymethyl)phenylcarbazole in 150 ml of benzene is added in portions 8.22 g (40 mmole) ofPCl₅. The mixture is stirred at about 10° for 15 minutes after which ahomogenous solution is obtained. Water (75 ml) is added in portions tothe benzene solution. The layers are separated and the organic layerwashed with H₂ O, dried over Na₂ SO₄, filtered and evaporated. The oilis treated with petroleum ether and the resulting solid is filtered anddried to yield 9.5 g (95%) of p-(carbazol-9-yl)benzylchloride, m.p.88°-89°.

C. Methyl D,L-3-[4-(carbazol-9-yl)phenyl]-2-isocyano-2-methyl propionate

A solution of 9.0 g (30 mmole) of p-(carbazol-9-yl)benzylchloridedissolved in 45 ml of DMF is stirred magnetically at -45°. To thissolution is added over 5-10 minutes, an anion solution prepared by theaddition of 5.8 g (51 mmole) of methyl 2-isocyanopropionate to 2.75 g(51 mmole) of sodium methoxide contained in 75 ml of DMF at -45°. Theresultant mixture is permitted to gradually rise to -15°. 700 ml of H₂ Ois then added and the mixture extracted with ethyl acetate. The ethylacetate layer is washed with H₂ O, dried over Na₂ SO₄, filtered andevaporated. The residue is washed with 3 × 50 ml petroleum ether toleave 6.2 g (56%) of methylD,L-3-[4-(carbazol-9-yl)phenyl]-2-isocyano-2-methyl propionate as an oilwhich can be used as such in the subsequent reaction. A samplerecrystallized from petroleum ether has m.p. 103°-105°.

D. D,L-4-(Carbazol-9-yl)-N-formyl-α-methylphenylalanine methyl ester

To a solution of 6.2 g (16.8 mmole) of methylD,L-3-[4-)carbazol-9-yl)phenyl]-2-isocyano-2-methyl propionate in 100 mlof ethyl acetate, cooled to 5° is added with stirring 1 ml of 12Nhydrochloric acid. After stirring for 15 minutes the solution is washedwith 2 × 50 ml of water. The organic layer is dried (Na₂ SO₄) andevaporated and the residue crystallized from benzene to yield 5 g (77%)of D,L-4-(carbazol-9-yl)-N-formyl-α-methylphenylalanine methyl ester,m.p. 167°-170°.

E. D,L-4-(Carbazol-9-yl)-α-methylphenylalanine

A mixture of 25 ml of 3N NaOH solution, 100 ml of methanol, and 3.0 g(7.7 mmole) of D,L-4-(carbazol-9-yl)-N-formyl-60 -methylphenylalaninemethyl ester is refluxed on a steam bath for 1.5 hours. The methanol isevaporated off and 50 ml of H₂ O added. The solution is then refluxed inan oil bath at 115° for 4 hours with a nitrogen atmosphere beingmaintained throughout hydrolysis. 27 ml of 3N HCl is added to the cooledsolution followed by 10 ml of 1N sodium acetate solution. The solid isfiltered, washed with water and dried overnight in a vacuum oven at 50°to yield 2.55 g (94%) of D,L-4-(carbazol-9-yl)-α-methylphenylalanine,m.p. 271°-274°.

EXAMPLE 61 D,L-3-(Imidazol-2-yl)-α-Methyltyrosine Dihydrochloride A.D,L-N-Formyl-α-Methyl-3-Thiocarbamoyltyrosine Methyl Ester

A solution of D,L-3-cyano-N-formyl-α-methyl-tyrosine methyl ester (1.5g.; 5.7 mmoles) prepared as described in Part D of Example 47, in 15 ml.pyridine and 2 ml. triethylamine is saturated with hydrogen sulfide andheated at 70° C. in a glass bomb for 18 hours. The reaction mixture isevaporated to dryness, dissolved in ethyl acetate, washed with water,dried and evaporated to dryness. The residue is dissolved in 10 ml.chloroform from which D,L-N-formyl-α-methyl-3-thiocarbamoyltyrosinemethyl ester (1.36 g.; 85%) crystallizes out; m.p. 177°-179° (dec.).

B. D,L-N-Formyl-α-Methyl-3-(Methylthiocarboximidato)-Tyrosine MethylEster

D,L-N-Formyl-α-methyl-3-thiocarbamoyltyrosine methyl ester from Part Aof Example 61 (14.75 g.; 50 mmoles) is suspended in 150 ml. acetone and4.35 ml. methyl fluorosulfonate is added. After 5 minutes, a solution isobtained and a temperature increase to 35° is observed. After stirring 2hours at room temperature, the solution is evaporated to dryness, theresidue is dissolved in water and the solution is extracted with ethylacetate. The aqueous layer is made basic with sodium bicarbonate andextracted with ethyl acetate. This extract is then dried and evaporatedto dryness to yield an oil that crystallizes when triturated in ether.Filtration affords 13.64 g. (88%) ofD,L-N-formyl-α-methyl-3-(methylthiocarboximidato)tyrosine methyl ester,m.p. 140°-143° (dec.).

C. D,L-3-(Imidazol-2-yl)-α-Methyltyrosine Dihydrochloride

D,L-N-Formyl-α-methyl-3-(methylthiocarboximidato)-tyrosine methyl ester(8 g.; 25.8 mmoles), amino acetaldehyde diethyl acetal (3.4 g.; 25.6mmoles), and oxalic acid (2.32 g.; 25.8 mmoles) in 200 ml. methanol isrefluxed for 2 hours. The resulting mixture is evaporated to dryness,water (200 ml) is added to dissolve the residue and the solution isextracted with ethyl acetate. The aqueous layer is basified with solidsodium bicarbonate and washed with 100 ml of ether, 20 ml of ethylacetate and evaporated to dryness. The residue from the aqueous solutionis stirred vigorously with 200 ml of chloroform, which, after separationand drying is evaporated to dryness to yield 10 g. of an oil.

The oil (8.4 g) is dissolved in 100 ml concentrated hydrochloric acid,and the mixture refluxed for one hour. Evaporation to dryness yieldsD,L-3-(imidazol-2-yl)-α-methyltyrosine dihydrochloride, m.p. 160°-175°(dec.) (4.7 g.; 70%).

EXAMPLE 62 D,L-2-Methyl-3-(2-Methanesulfonylamidobenzimidazol-5-yl)Alanine Dihydrochloride Hemihydrate

D,L-N-Formyl-3,4-diamino-α-methylphenylalanine methyl ester (4.0 g.; 16mm) (prepared as in Step C of Example 26) and methylN-methanesulfonylimino dithio carbonate (2.4 g.; 19.6 mmoles) in 20 ml.dimethyl formamide is heated overnight in an oil bath at 150° . Thesolvent is evaporated to a thick oil from which 2.37 g. (42%)D,L-N-formyl-2-methyl-3-(2-methanesulfonylamidobenzimidazol-5-yl)alaninemethyl ester is isolated as a solid, m.p. 220°-225° (dec.) ontrituration with 10 ml. ethanol. This ester (1 g.; 2.82 mmoles) isrefluxed in 20 ml. concentrated hydrochlorice acid for 75 minutes. It isthen cooled and evaporated under vacuum. The residue is redissolvedagain in water and taken back to dryness. This operation is repeatedonce more with water and then twice with ethanol to yieldD,L-2-methyl-3-(3-methanesulfonylamidobenzimidazol-5-yl)alaninedihydrochloride hemihydrate (680 mg.; 61%) m.p. 250°-251° (dec.).

EXAMPLE 63 D,L-2-Methyl-3-(2-amino-4-pyridyl)alaninedihydrochloride A.7-Bromomethyl tetrazolo[1,5-a]pyridine

7-Methyl tetrazolo[1,5-a]pyridine [Boyer, et al., J. AM. Chem. Soc., 82,2218 (1960] (23 g, 173 mmole), N-bromosuccinimide (30.6 g, 173 mmole)and benzoyl peroxide (100 mg) in 1.5 liters of benzene is refluxedovernight. More N-bromosuccinimide (15.3 g, 86.5 mole) is added and thereflux is maintained for several hours. The mixture is cooled and washedwith 100 ml 20% sodium hydroxide and then with water. It is dried overcalcium chloride, evaporated to dryness to yield 36.4 g of a mixture of7-bromomethyltetrazolo [1,5-a]pyridine (63%) 7-dibromomethyltetrazolo[1,5-a]pyridine (24% ) and 7-methyltetrazolo [1,5-a]pyridine (13% ). Twotriturations of this mixture with 500 ml of ether-hexane 1:1 (v/v)affords 25 g of a mixture consisting of 82% monobromo derivative, 13%dibromo derivative and 5% of starting material. This mixture is used forthe next step.

B. D,L-N-Formyl-2-methyl-3-(tetrazolo[1,5-a]pyrid-7-yl) alanine methylester

Freshly prepared sodium methoxide (6 g, 113 mmole) is disolved in 100 mldimethyl formamide and then cooled with an ice-bath to an internaltemperature of 0°-5° . To this solution is added methyl2-isocyanopropionate (12.8 g, 113 mmole). This solution is then addedslowly to a solution of 7-bromomethyltetrazolo [1,5-a] pyridine (25 g ofmixture; 94 mmole) in 40 ml of dimethyl formamdide and maintaining theinternal temperature around 5°. After the addition the mixture isallowed to warm up to room temperature. It is then poured into 1.5liters of water and then extracted five times with 600 ml ethyl acetate.The ethyl acetate layers are combined, washed several times with waterand dried over sodium sulfate. The dried solution is treated withcharcoal and the volume is reduced to 1.5 liters. This solution is thentreated with 1.5 ml concentrated hydrochloric acid at room temperaturefor 75 minutes. Water is added and decanted; the organic layer is washedwith 5% sodium bicarbonate, with water and then dried over calciumchloride. The solution is evaporated to dryness and trituration withether leaves 8.45 g (34%) ofD,L-N-formyl-2-methyl-3-(tetrazolo]1,5-a]pyrid-7-yl) alanine methylester, m.p. 80°-85° .

C. D,L-2-Methyl-3-(2-amino-4-pyridyl)alanine dihydrochloride

D,L-N-Formyl-2-methyl-3-(tetrazolo[1,5-a]pyrid-7-yl)alanine methyl ester(4 g, 15.2 mmole) dissolved in 60 ml hydrochloric acid is heated on asteam bath until all starting material has disappeared as seen by TLC.Stannous chloride dihydrate (10.25 g, 45.6 mmole) is added in portions.The first additions give strong gas evolution. The mixture is thenheated on steam bath for 105 minutes, after which is is evaporated todryness. The residue is dissolved in 120 ml of water and hydrogensulfide is bubbled through the solution. The precipitate filtered andthe filtrate is treated with hydrogen sulfide again. The solid isfiltered again and the filtrate is evaporated to dryness. The residue istriturated with 50 ml acetonitrile and filtration yields 2.66 g (66%) ofD,L,-2-methyl-3-(2-amino-4-pyridyl)alanine dihydrochloride, m.p.258°-260° .

EXAMPLE 64 D,L-2-Methyl-3-(tetrazolo[1,5-a]pyrid-7-yl)alaninehydrochloride

D,L,N-Formyl-2-methyl-3-(tetrazolo[1,5-a]pyrid-7-yl)alanine methyl ester(4.0 g, 15.2 mmole), prepared as in part B of Example 63, is refluxed in50 ml concentrated hydrochloric acid for 5 hours. On cooling, some solidimpurities are filtered and discarded. The filtrate is taken down todryness, redissolved in 200 ml water and left in the refrigerator for 18hours. The solid is removed by filtration, the filtrate is treated withactivated charcoal and then evaporated to dryness. The residue istriturated with 50 ml hot isopropanol and filtered to yield 2.37 g (60%)of D,L,-2-methyl-3-(tetrazolo[1,5-a]pyrid-7-yl)alanine hydrochloride,m.p. 240°-245° .

EXAMPLE 65 D,L-3-cyano-α-methylphenylalanine methyl ester hydrochloride

A solution of 56 g (0.245 mole) of methylD,L-3-(3-cyanophenyl)-2-isocyano-2-methyl propionate (prepared as inpart A of Example 2) in 500 ml of ethyl acetate is cooled in an icebath. To the cooled and stirred solution is added 23 ml of concentratedhydrochloric acid, the ice bath is removed and the mixture stirred at25° for 2 hours. The solution is washed with 3 × 200 ml of water and theaqueous extract is made basic with solid sodium carbonate. Extraction ofthe basic solution with 2 × 100 ml of ether, drying of the etheralextract and passage of gaseous hydrogen chloride into the dried ethersolution gives a precipitate which is filtered and dried to yield 4.27 g(6.9%) of D,L-3-cyano-α-methylphenylalanine methyl ester hydrochloride,m.p. 160°-165° .

EXAMPLE 66 D,L-α-Methyl-3-(4-trifluoromethylthiazol-2-yl)tyrosinehydrochloride A.D,L-3-(4,5-Dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-N-formyl-.alpha.-methyltyrosinemethyl ester

A mixture of 3.5 g (18 mm) of 3-bromo-1,1,1-trifluoropropanone, 150 mlof acetonitrile and 5 g (17 mm) ofD,L,N-formyl-α-methyl-3-thiocarbamoyltyrosine methyl ester, described inpart A of Example 61, is magnetically stirred at reflux for 30 minutes.The solution is evaporated to dryness and the gummy residue trituratedwith ethyl acetate. The product is filtered and washed with a smallvolume of diethyl ether to yield 7.5 g of crude (97%)D,L-3-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-N-formyl-.alpha.-methyltyrosinemethyl ester which is of sufficient quality for the next step.

B. D,L-α-Methyl-3-(4-trifluoromethylthiazol-2-yl)tyrosine hydrochloride

A mixture of 100 ml of concentrated HCl and 7.5 g (18 mm) ofD,L,-3-(4,5-dihydro-4-hydroxy-4-trifluoromethylthiazol-2-yl)-N-formyl-.alpha.-methyltyrosinemethyl ester is refluxed for one hour. After cooling, the crystals arefiltered and washed with diethyl ether. The solid is dried at 50° undervacuum for 3 hours to yield 3.4 g (50%) ofD,L-α-methyl-3-(4-trifluoromethylthiazol-2-yl)tyrosine hydrochloride,m.p. 285° (dec.).

EXAMPLE 67 PREPARATION OF CAPSULE FORMULATION

                  EXAMPLE 67                                                      ______________________________________                                        PREPARATION OF CAPSULE FORMULATION                                                                 Milligrams per                                           Ingredient           Capsule                                                  ______________________________________                                        α-Methyl-3-(4-trifluoromethyl-                                                               40                                                        thiazol-2-yl)phenylalanine                                                   Starch               440                                                      Magnesium stearate   5                                                        ______________________________________                                    

The active ingredient, starch and magnesium stearate are blendedtogether. The mixture is used to fill hard shell capsules of a suitablesize at a fill weight of 485 milligrams per capsule.

EXAMPLE 68 PREPARATION OF TABLET FORMULATION

                  EXAMPLE 68                                                      ______________________________________                                        PREPARATION OF TABLET FORMULATION                                                                Milligrams per                                             Ingredient         Tablet                                                     ______________________________________                                        4-(Imidazol-2-yl)-α-methyl-                                                                25                                                          phenylalanine                                                                Lactose            200                                                        Corn starch (for mix)                                                                            50                                                         Corn starch (for paste)                                                                          50                                                         Magnesium stearate 6                                                          ______________________________________                                    

The active ingredient, lactose and corn starch (for mix), are blendedtogether. The corn starch (for paste) is suspended in water at a ratioof 10 grams of corn starch per 80 milliliters of water and heated withstirring to form a paste. This paste is then used to granulate the mixedpowders. The wet granules are passed through a No. 8 screen and dried at120° F. The dry granules are passed through a No. 16 screen. The mixtureis lubricated with magnesium stearate and compressed into tablets in asuitable tableting machine. Each tablet contains 25 milligrams of activeingredient.

EXAMPLE 69 PREPARATION OF ORAL SYRUP FORMULATION

                  EXAMPLE 69                                                      ______________________________________                                        PREPARATION OF ORAL SYRUP FORMULATION                                         Ingredient             Amount                                                 ______________________________________                                        α-Methyl-4-(pyrrol-1-yl)phenylalanine                                                          50       mg.                                           Sorbitol solution (70% N.F.)                                                                         40       ml.                                           Sodium benzoate        150      mg.                                           Saccharin              50       mg.                                           Red Dye (F.D. & C. No. 40)                                                                           10       mg.                                           Cherry flavor          50       mg.                                           Distilled water qs to  100      ml.                                           ______________________________________                                    

The sorbitol solution is added to 40 milliliters of distilled water andthe active ingredient is suspended therein. The saccharin, sodiumbenzoate, flavor and dye are added and dissolved in the above solution.The volume is adjusted to 100 milliliters with distilled water.

Other ingredients may replace those listed in the above formulation. Forexample, a suspending agent such as bentonite magma, tragacanth,carboxymethylcellulose or methylcellulose may be used. Phosphates,citrates or tartrates may be added as buffers. Preservatives may includethe parabens, sorbic acid and the like and other flavors and dyes may beused in place of those listed above.

What is claimed is:
 1. A compound of the formula ##STR10## wherein R¹and R² are hydrogen or lower alkyl and R³ is a substituted benzene ringof the formula ##STR11## wherein Y₁ is hydrogen, cyanoamino, carboxyl,cyano, thiocarbamoyl, aminomethyl, guanidino, hydroxy,methanesulfonamido, nitro, amino, methanesulfonyloxy, carboxymethoxy, ormethoxy and Y₂ is a substituted or unsubstituted 5-membered heterocyclicring containing one or more nitrogen atoms.
 2. A composition useful fortreating hypertension comprising a therapeutically effective amount of acompound of claim 1 in combination with a pharmaceutically acceptablecarrier.
 3. A compound according to claim 1 whichisα-methyl-4-(pyrrol-1-yl)-phenylalanine,4-(2-aminoimidazol-1-yl)-α-methylphenylalanine,4-(imidazol-2-ylamino)-α-methylphenylalanine,4-(imidazol-2-yl)-α-methylphenylalanine,4-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine,3-(imidazol-2-yl)-α-methylphenylalanine,3-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine,4-(imidazol-4-yl)phenylalanine,4-(4,5-dihydroimidazol-2-yl)phenylalanine,3-(imidazol-2-yl)phenylalanine, 4-(pyrrol-1-yl)phenylalanine,4-[2-(carboxy)pyrrol-1-yl]-α-methylphenylalanine,α-methyl-3-(pyrrol-1-yl)phenylalanine,3-hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalanine,3-methoxy-α-methyl-4-(pyrrol-1-yl)phenylalanine,α-methyl-3-(pyrrol-1-yl)tyrosine,4-methoxy-α-methyl-3-(pyrrol-1-yl)phenylalanine or3-(imidazol-2-yl)-α-methyltyrosine,
 4. A compound according to claim 3which isα-methyl-4-(pyrrol-1-yl)phenylalanine,4-(2-aminoimidazol-1-yl)-α-methylphenylalanine,4-(imidazol-2-ylamino)-α-methylphenylalanine,4-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine,4-(imidazol-2-yl)-α-methylphenylalanine,3-(imidazol-2-yl)-α-methylphenylalanine,3-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine,4-(imidazol-2-yl)phenylalanine,4-(4,5-dihydroimidazol-2-yl)phenylalanine,3-(imidazol-2-yl)phenylalanine, 4-(pyrrol-1-yl)phenylalanine,α-methyl-3-(pyrrol-1-yl)phenylalanine,3-hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalanine,3-methoxy-α-methyl-4-(pyrrol-1-yl)phenylalanine,α-methyl-3-(pyrrol-1-yl)tyrosineor 3-(imidazol-2-yl)-α-methyltyrosine.5. A compound according to claim 4 whichisα-methyl-4-(pyrrol-1-yl)phenylalanine,4-(imidazol-2-yl)-α-methylphenylalanine,4-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine,3-(imidazol-2-yl)-α-methylphenylalanine,3-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine,4-(imidazol-2-yl)phenylalanine,4-(4,5-dihydroimidazol-2-yl)phenylalanine,3-(imidazol-2-yl)phenylalanine, 4-(pyrrol-1-yl)phenylalanine,α-methyl-3-(pyrrol-1-yl)phenylalanine,3-hydroxy-α-methyl-4-(pyrrol-1-yl)phenylalanine,3-methoxy-α-methyl-4-(pyrrol-1-yl)phenylalanine,α-methyl-3-(pyrrol-1-yl)tyrosine,or 3-(imidazol-2-yl)-α-methyltyrosine.6. A compound according to claim 5 whichisα-methyl-4-(pyrrol-1-yl)phenylalanine,4-(imidazol-2-yl)-α-methylphenylalanine or4-(4,5-dihydroimidazol-2-yl)-α-methylphenylalanine.
 7. A compound ofclaim 1 wherein Y₁ is hydrogen, hydroxy or methoxy and Y₂ is asubstituted or unsubstituted 5-membered heterocyclic ring containing oneor more nitrogen atoms.
 8. A compound of claim 7 wherein Y₂ ispyrrol-1-yl, 2-carboxypyrrol-1-yl, 2-aminoimidazol-1-yl,imidazol-2-ylamino, imidazol-2-yl or 4,5-dihydroimidazol-2-yl.
 9. Thecompound of claim 7 wherein Y₂ is pyrrol-1-yl or imidazol-1-yl.
 10. Thecompound of claim 7 wherein Y₂ is imidazolyl.
 11. The compound of claim7 wherein Y₂ is pyrrol-1-yl.
 12. The compound of claim 11 wherein Y₁ isH or hydroxy.
 13. The compound of claim 12 where Y₁ is H.
 14. Thecompound of claim 13 having the formula ##STR12##